Method of making wire bond vias and microelectronic package having wire bond vias

ABSTRACT

Microelectronic components and methods forming such microelectronic components are disclosed herein. The microelectronic components may include a plurality of electrically conductive vias in the form of wire bonds extending from a bonding surface of a substrate, such as surfaces of electrically conductive elements at a surface of the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application incorporates by reference herein the commonlyowned application of Zhao et al., entitled “Microelectronic PackageHaving Wire Bond Vias and Stiffening Layer” filed on even date herewith.

BACKGROUND OF THE INVENTION

The subject matter of the present application relates to the packagingof a microelectronic element and related circuitry, for example, amethod of making a structure, e.g., microelectronic package having aplurality of electrically conductive vias in form of wire bondsextending from bonding surfaces of the substrate, such as surfaces ofelectrically conductive elements at a surface of a substrate.

Microelectronic devices such as semiconductor chips typically requiremany input and output connections to other electronic components. Theinput and output contacts of a semiconductor chip or other comparabledevice are generally disposed in grid-like patterns that substantiallycover a surface of the device (commonly referred to as an “area array”)or in elongated rows which may extend parallel to and adjacent each edgeof the device's front surface, or in the center of the front surface.Typically, devices such as chips must be physically mounted on asubstrate such as a printed circuit board, and the contacts of thedevice must be electrically connected to electrically conductivefeatures of the circuit board.

Semiconductor chips are commonly provided in packages that facilitatehandling of the chip during manufacture and during mounting of the chipon an external substrate such as a circuit board or other circuit panel.For example, many semiconductor chips are provided in packages suitablefor surface mounting. Numerous packages of this general type have beenproposed for various applications. Most commonly, such packages includea dielectric element, commonly referred to as a “chip carrier” withterminals formed as plated or etched metallic structures on thedielectric. These terminals typically are connected to the contacts ofthe chip itself by features such as thin traces extending along the chipcarrier itself and by fine leads or wires extending between the contactsof the chip and the terminals or traces. In a surface mountingoperation, the package is placed onto a circuit board so that eachterminal on the package is aligned with a corresponding contact pad onthe circuit board. Solder or other bonding material is provided betweenthe terminals and the contact pads. The package can be permanentlybonded in place by heating the assembly so as to melt or “reflow” thesolder or otherwise activate the bonding material.

Many packages include solder masses in the form of solder balls,typically about 0.1 mm and about 0.8 mm (5 and mils) in diameter,attached to the terminals of the package. A package having an array ofsolder balls projecting from its bottom surface is commonly referred toas a ball grid array or “BGA” package. Other packages, referred to asland grid array or “LGA” packages are secured to the substrate by thinlayers or lands formed from solder. Packages of this type can be quitecompact. Certain packages, commonly referred to as “chip scalepackages,” occupy an area of the circuit board equal to, or onlyslightly larger than, the area of the device incorporated in thepackage. This is advantageous in that it reduces the overall size of theassembly and permits the use of short interconnections between variousdevices on the substrate, which in turn limits signal propagation timebetween devices and thus facilitates operation of the assembly at highspeeds.

Packaged semiconductor chips are often provided in “stacked”arrangements, wherein one package is provided, for example, on a circuitboard, and another package is mounted on top of the first package. Thesearrangements can allow a number of different chips to be mounted withina single footprint on a circuit board and can further facilitatehigh-speed operation by providing a short interconnection betweenpackages. Often, this interconnect distance is only slightly larger thanthe thickness of the chip itself. For interconnection to be achievedwithin a stack of chip packages, it is necessary to provide structuresfor mechanical and electrical connection on both sides of each package(except for the topmost package). This has been done, for example, byproviding contact pads or lands on both sides of the substrate to whichthe chip is mounted, the pads being connected through the substrate byconductive vias or the like. Solder balls or the like have been used tobridge the gap between the contacts on the top of a lower substrate tothe contacts on the bottom of the next higher substrate. The solderballs must be higher than the height of the chip in order to connect thecontacts. Examples of stacked chip arrangements and interconnectstructures are provided in U.S. Patent App. Pub. No. 2010/0232129 (“the'129 Publication”), the disclosure of which is incorporated by referenceherein in its entirety.

Microcontact elements in the form of elongated posts or pins may be usedto connect microelectronic packages to circuit boards and for otherconnections in microelectronic packaging. In some instances,microcontacts have been formed by etching a metallic structure includingone or more metallic layers to form the microcontacts. The etchingprocess limits the size of the microcontacts. Conventional etchingprocesses typically cannot form microcontacts with a large ratio ofheight to maximum width, referred to herein as “aspect ratio”. It hasbeen difficult or impossible to form arrays of microcontacts withappreciable height and very small pitch or spacing between adjacentmicrocontacts. Moreover, the configurations of the microcontacts formedby conventional etching processes are limited.

Despite all of the above-described advances in the art, still furtherimprovements in making and testing microelectronic packages would bedesirable.

BRIEF SUMMARY OF THE INVENTION

Disclosed herein are microelectronic elements and a method ofmanufacturing microelectronic elements.

In an embodiment, a method of forming a plurality of wire bondsconnected to a substrate may include positioning at least one of abonding tool and a portion of a wire extending downward beyond a facethereof or a forming surface relative to one another such that an end ofthe wire portion extending downward beyond a face of the bonding tool ispositioned at a greater depth from the bonding tool face than theforming surface. The wire portion may be a first wire portion and theextending of the first wire portion may be performed by bonding a secondportion of the wire to a second bonding surface, and then moving thebonding tool face to a greater height above a plane in which the secondbonding surface lies such that the first wire portion may be extendedoutward beyond the face of the bonding tool, and then severing the wireto separate the first wire portion from the second wire portion. Thestep of severing the wire may include clamping the wire and tensioningthe clamped wire to cause the clamped wire to break at the boundarybetween the first and second wire portions. The step of severing thewire may include clamping the wire and tensioning the clamped wire tocause the clamped wire to break between the first and second wireportions, to break at a predetermined length, and/or may includeclamping and tensioning a plurality of wires to cause the clamped wiresto break at a plurality of different predetermined lengths.

The bonding tool may be moved along the first forming surface in a firstdirection parallel to the face of the bonding tool so as to bend thewire portion towards the bonding tool. The bonding surface may beexposed at a surface of a substrate when the step of using the bondingtool is performed to bond the coined surface to the bonding surface. Amicroelectronic element may be mounted and electrically interconnectedwith the substrate such that the microelectronic element is electricallyinterconnected with at least some of the wire bonds.

The first forming surface may include a groove and the step of movingthe bonding tool along the first forming surface may include moving thebonding tool face in the first direction along a length of the groovesuch that at least a part of the wire portion moves within the groove.The first forming surface may be a surface of a forming element havingan opening therein, and the step of positioning may include positioningthe bonding tool such that the wire portion extends at least partiallyinto the opening. The opening may include a tapered portion adjacent tothe first forming surface, and the tapered portion may be configured toguide the wire portion towards a predetermined location of the firstforming surface. The first forming surface may be a surface of a formingelement having an opening therein. The step of positioning may includepositioning the bonding tool such that the wire portion extends at leastpartially into the opening. The opening may include a tapered portionadjacent to the first forming surface, and the tapered portion may beconfigured to guide the wire portion into the groove.

The step of moving the bonding tool may include moving the bonding toolinto the opening such that the wire portion extends at least partiallyinto the opening. The coining surface may be disposed within theopening. The coining surface may include a groove having a depth that isless than a diameter of the wire portion. The opening may be a firstopening, and the forming element includes a second opening. The step ofmoving the bonding tool may include moving the bonding tool into thesecond opening such that the wire portion extends at least partiallyinto the second opening. The coining surface may be disposed within thesecond opening.

A first wire bond of the wire bonds may be adapted for carrying a firstsignal electric potential, and a second wire bond of the wire bonds maybe adapted for simultaneously carrying a second signal electricpotential different from first signal electric potential. At least twoof the wire bonds may be bonded to a single bonding surface of theplurality of bonding surfaces. This may improve the tolerance of thefree ends of the wire bonds. For example, in the disclosed embodiments,the pitch of the free ends of the wire bonds may be 150, 200, 300, or400 micrometers from one another, and may differ in the x or ydirections of the Cartesian coordinate system. The pitch of the freeends of the wire bonds may be at 150 or 200, and may have a 3-sigmatolerance, i.e., three standard deviations away from the center of thedistribution, for the free ends that is less than +/−25 micrometers.

The bonding tool may then be moved in a second direction transverse tothe bonding tool face such that an exposed wall of the bonding toolextending away from the bonding tool face confronts a second formingsurface extending away from the first forming surface. The first andsecond forming surfaces may be disposed at a forming station and thesteps of moving of the bonding tool in the first and second directionsmay be performed at the forming station. The second forming surface mayslope away from the first forming surface at a first angle to the firstforming surface, and the exposed bonding tool wall may slope away fromthe bonding tool face at the first angle. The second forming surface maybe a channel recessed relative to at least one third surface. The stepof using the bonding tool may be performed at a bonding station. Thebonding tool may be supported by a bond head, and prior to coining apart of the wire portion, moving the bond head and the bonding toolsupported thereby from the forming station to the bonding station. Thewire portion may be bent towards the exposed wall of the bonding tool.

Part of the wire portion between the bonding tool face and a coiningsurface may be coined. The coining surface may be disposed at theforming station and the step of coining a part of the wire portionbetween the bonding tool face and the coining surface may be performedat the forming station. The coined part may have resistance to movementin the lateral direction when the step of using the bonding tool isperformed to bond the wire portion to the bonding surface. The coinedpart of the wire portion may have a flat surface, and the step of usingthe bonding tool may bond the flat surface of the coined part to thebonding surface, and may place a permanent plastic kink in the wire. Thecoined part of the wire portion may have a patterned face of raised andrecessed features, and the step of using the bonding tool may bond thepatterned face of the coined part to the bonding surface.

The bonding tool may be used to bond the coined part of the wire portionto an electrically conductive bonding surface of the substrate to form awire bond, while leaving unbounded the end of the wire portion remotefrom the coined part. The bonding tool may have a capillary out of whichthe wire portion extends and the face of the bonding tool may be theface of the capillary. The bonding tool may be an ultrasonic bondingtool out of which the wire portion extends and the face of theultrasonic bonding tool is the face of the bonding tool. The ultrasonicbonding tool is a wedge-bonding tool. The bonding tool and the formingsurfaces may be assembled with a common bond head. Such steps may berepeated to form a plurality of the wire bonds to at least one of thebonding surface.

After forming the plurality of wire bonds, an encapsulation layeroverlying the one or more bonding surfaces may be formed. Theencapsulation layer may be formed so as to at least partially cover thebonding surface and the wire bonds. An unencapsulated portion of eachwire bond may be defined by a portion of at least one of an end surfaceof such wire bond or of an edge surface of such wire bond that isuncovered by the encapsulation layer.

A microelectronic package may include a component, such as a substrate,having a first surface and a second surface opposite from the firstsurface. The first surface of the component may have a first region anda second region. The microelectronic element may overly the firstregion. The electrically conductive elements may be exposed at at leastone of the first or second surfaces of the component within the secondregion. The encapsulation layer may overly at least the second region ofthe component. The unencapsulated portions of the wire bonds may includethe ends of the wire bonds. A first wire bond of the wire bonds may beconfigured to carry a first signal electric potential and a second wirebond of the wire bonds may be configured to simultaneously carry asecond signal electric potential different from the first signalelectric potential. Each wire bond may have an edge surface extendinglongitudinally to the end of such wire bond, and the unencapsulatedportions of the wire bonds may be defined by the ends of the wire bondsand portions of the edge surfaces adjacent the ends that are uncoveredby the encapsulation layer. The unencapsulated portion of at least oneof the wire bonds may overly a major surface of the microelectronicelement. An end of at least one of the wire bonds may be displaced in adirection parallel to the first surface of the substrate from its baseby at least a distance equal to one of a minimum pitch between adjacentconductive elements of the plurality of conductive elements, and 100micrometers. At least one of the wire bonds may include at least onebend between the unencapsulated portion thereof and the conductiveelement to which the at least one wire bond is joined. The bend of theat least one wire bond is remote from the unencapsulated portion thereofand the conductive element to which the at least one wire bond isjoined. The unencapsulated portion of the at least one wire bond mayoverly a major surface of the microelectronic element. The wire bondsmay be joined to the conductive elements at positions in a first patternhaving a first minimum pitch between adjacent ones of the conductiveelements. The unencapsualted portions of the wire bonds may be disposedat positions in a second pattern having a second minimum pitch betweenadjacent unencapsulated portions of wire bonds of the plurality of wirebonds. The second minimum pitch may be greater than the first pitch. Theat least one microelectronic element may include first and secondmicroelectronic elements overlying the first surface within the firstregion. At least some of the conductive elements may be electricallyconnected with the first microelectronic element. At least some of theconductive elements may be electrically connected with the secondmicroelectronic element. The first microelectronic element and thesecond microelectronic elements may be electrically connected with oneanother within the microelectronic package. At least one of the firstconductive elements may have at least two of the wire bonds joinedthereto.

At least one microelectronic element may overly the first surface.Electrically conductive elements may be exposed at at least one of thefirst surface or the second surface of the substrate. At least some ofthe conductive elements may be electrically connected with the least onemicroelectronic element. A plurality of wire bonds may each have acoined portion joined to a conductive element of the conductiveelements. An uncoined portion may extend in a longitudinal directionaway from the coined portion. A transition portion may connect theuncoined and coined portions. The coined portion may have a width in alateral direction transverse to the longitudinal direction greater thana width of the uncoined portion. The transition portion may have a widthdecreasing with proximity to the uncoined portion. The wire bonds mayhave ends remote from the coined portions of the respective wire bondsand the component. An encapsulation layer may extend from at least oneof the first or second surfaces, and may cover portions of the wirebonds such that covered portions of the wire bonds are separated fromone another by the encapsulation layer. Unencapsulated portions of thewire bonds may be defined by portions of the wire bonds which are notcovered by the encapsulation layer. At least parts of the uncoinedportions may have a cylindrical shape. The ends of at least some of thewire bonds may be uncovered by the encapsulation layer.

These and other embodiments of the present disclosure are more fullydescribed hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is sectional view depicting a microelectronic package accordingto an embodiment of the invention;

FIG. 2 shows a top plan view of the microelectronic package of FIG. 1;

FIG. 3 is a sectional view depicting a microelectronic package accordingto a variation of the embodiment shown in FIG. 1;

FIG. 4 is a sectional view depicting a microelectronic package accordingto a variation of the embodiment shown in FIG. 1;

FIG. 5A is a sectional view depicting a microelectronic packageaccording to a variation of the embodiment shown in FIG. 1;

FIG. 5B is a fragmentary sectional view depicting a conductive elementformed on an unencapsulated portion of a wire bond according to anembodiment of the invention;

FIG. 5C is a fragmentary sectional view depicting a conductive elementformed on an unencapsulated portion of a wire bond according to avariation of that shown in FIG. 5B;

FIG. 5D is a fragmentary sectional view depicting a conductive elementformed on an unencapsulated portion of a wire bond according to avariation of that shown in FIG. 5B;

FIG. 6 is a sectional view illustrating a microelectronic assemblyincluding a microelectronic package according to one or more of theforegoing embodiments and an additional microelectronic package and acircuit panel electrically connected thereto;

FIG. 7 is a top elevation view illustrating a microelectronic packageaccording to an embodiment of the invention;

FIG. 8 is a fragmentary top elevation view further illustrating amicroelectronic package according to an embodiment of the invention;

FIG. 9 is a top elevation view illustrating a microelectronic packageincluding a lead frame type substrate according to an embodiment of theinvention;

FIG. 10 is a corresponding sectional view of the microelectronic packageshown in FIG. 9;

FIG. 11 is a sectional view of a microelectronic assembly including aplurality of microelectronic packages electrically connected togetherand reinforced with an underfill according to a variation of theembodiment shown in FIG. 6;

FIG. 12 is a photographic image representing an assembly having bondsbetween wire bonds of a first component and solder masses of a secondcomponent attached thereto;

FIG. 13A is a fragmentary sectional view illustrating a wire bond via ina microelectronic package according to an embodiment of the invention;

FIG. 13B is a fragmentary sectional view illustrating a wire bond via ina microelectronic package according to an embodiment of the invention;

FIG. 13C is an enlarged fragmentary sectional view illustrating a wirebond via in a microelectronic package according to the embodiment shownin FIG. 13B;

FIG. 13D is a fragmentary sectional view illustrating a wire bond via ina microelectronic package according to an embodiment of the invention;

FIG. 13E is an enlarged fragmentary sectional view illustrating a wirebond via in a microelectronic package according to the embodiment shownin FIG. 13D;

FIG. 13F is a fragmentary sectional view illustrating a wire bond via ina microelectronic package according to an embodiment of the invention;

FIG. 14A illustrates stages in a method of forming a metal wire segmentprior to bonding the wire segment to a conductive element according toan embodiment of the invention;

FIG. 14B is a fragmentary plan view of a shaped wire portion from aposition below a capillary face;

FIG. 14C is a sectional view of the shaped wire portion between thecapillary face and the coining surface;

FIG. 15 further illustrates a method as depicted in FIG. 14 and aforming unit suitable for use in such method;

FIGS. 16A-16D are plan views illustrating movement of a bond toolrelative to a forming element during shaping of a wire portion inaccordance with an embodiment of the invention;

FIG. 16E is a top elevation view illustrating wire bonds formedaccording to an embodiment of the invention;

FIGS. 17A, 17B and 17C are views from above a wirebonding assembly,further illustrating a process of shaping a wire portion and bonding theshaped wire portion according to an embodiment of the invention;

FIGS. 18A, 18B and 18C are views from above a wirebonding assembly,further illustrating a process of shaping a wire portion and bonding theshaped wire portion according to an embodiment of the invention;

FIG. 19 illustrates stages in a method of forming a metal wire segmentprior to bonding the wire segment to a conductive element according toan embodiment of the invention;

FIGS. 20A and 20B are sectional views illustrating one stage and anotherstage subsequent thereto in a method of forming an encapsulation layerof a microelectronic package according to an embodiment of theinvention;

FIG. 20C is an enlarged sectional view further illustrating the stagecorresponding to FIG. 19;

FIG. 21A is a sectional view illustrating a stage of fabricating anencapsulation layer of a microelectronic package according to anembodiment of the invention;

FIG. 21B is a sectional view illustrating a stage of fabricating anencapsulation layer of a microelectronic package subsequent to the stageshown in FIG. 21A;

FIGS. 22A-22E illustrate yet another method of forming an encapsulationlayer by molding in which unencapsulated portions of wire bonds protrudethrough the encapsulation layer.

FIGS. 23A and 23B are fragmentary sectional views illustrating wirebonds according to another embodiment;

FIGS. 24A and 24B are sectional views of a microelectronic packageaccording to a further embodiment.

FIGS. 25A and 25B are sectional views of a microelectronic packageaccording to a further embodiment;

FIG. 26 shows a sectional view of a microelectronic package according toanother embodiment;

FIGS. 27A-C are sectional views showing examples of embodiments ofmicroelectronic packages according to further embodiments;

FIGS. 28A-D show various embodiments of microelectronic packages duringsteps of forming a microelectronic assembly according to an embodimentof the disclosure;

FIG. 29 shows another embodiment of microelectronic packages duringsteps of forming a microelectronic assembly according to an embodimentof the disclosure;

FIGS. 30 A-C show embodiments of microelectronic packages during stepsof forming a microelectronic assembly according to another embodiment ofthe disclosure;

FIGS. 31A-C show embodiments of microelectronic packages during steps offorming a microelectronic assembly according to another embodiment ofthe disclosure;

FIGS. 32A and 32B show a portion of a machine that can be used informing various wire bond vias in various stages of a method accordingto another embodiment of the present disclosure;

FIG. 33 shows a portion of a machine that can be used in forming variouswire bond vias according in a method according to another embodiment ofthe present disclosure;

FIGS. 34A-C show various forms of an instrument that can be used in amethod for making wire bonds according to an embodiment of the presentdisclosure;

FIG. 35 shows a portion of a machine that can be used in forming variouswire bond vias according in a method according to another embodiment ofthe present disclosure;

FIG. 36 shows a portion of a machine that can be used in forming variouswire bond vias according in a method according to another embodiment ofthe present disclosure;

FIGS. 37 A-D show sectional views illustrating stages of fabricating amicroelectronic package according to an embodiment of the presentdisclosure;

FIGS. 38A and 38B show sectional views illustrating stages offabricating a microelectronic package according to another embodiment ofthe present disclosure; and

FIGS. 39A-C show sectional views illustrating stages of fabricating amicroelectronic package according to another embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Turning now to the figures, where similar numeric references are used toindicate similar features, there is shown in FIG. 1 a microelectronicassembly 10 according to an embodiment of the present invention. Theembodiment of FIG. 1 is a microelectronic assembly in the form of apackaged microelectronic element such as a semiconductor chip assemblythat is used in computer or other electronic applications.

The microelectronic assembly 10 of FIG. 1 includes a substrate 12 havinga first surface 14 and a second surface 16. The substrate 12 typicallyis in the form of a dielectric element, which is substantially flat. Thedielectric element may be sheet-like and may be thin. In particularembodiments, the dielectric element can include one or more layers oforganic dielectric material or composite dielectric materials, such as,without limitation: polyimide, polytetrafluoroethylene (“PTFE”), epoxy,epoxy-glass, FR-4, BT resin, thermoplastic, or thermoset plasticmaterials. The substrate may be a substrate of a package havingterminals for further electrical interconnection with a circuit panel,e.g., a circuit board. Alternatively, the substrate can be a circuitpanel or circuit board. In one example thereof, the substrate can be amodule board of a dual-inline memory module (“DIMM”). In yet anothervariation, the substrate can be a microelectronic element such as may beor include a semiconductor chip embodying a plurality of active devices,e.g., in form of an integrated circuit or otherwise.

The first surface 14 and second surface 16 are preferably substantiallyparallel to each other and are spaced apart at a distance perpendicularto the surfaces 14,16 defining the thickness of the substrate 12. Thethickness of substrate 12 is preferably within a range of generallyacceptable thicknesses for the present application. In an embodiment,the distance between the first surface 14 and the second surface 16 isbetween about 25 and 500 μm. For purposes of this discussion, the firstsurface 14 may be described as being positioned opposite or remote fromsecond surface 16. Such a description, as well as any other descriptionof the relative position of elements used herein that refers to avertical or horizontal position of such elements is made forillustrative purposes only to correspond with the position of theelements within the Figures, and is not limiting.

In a preferred embodiment, substrate 12 is considered as divided into afirst region 18 and a second region 20. The first region 18 lies withinthe second region and includes a central portion of the substrate 12 andextends outwardly therefrom. The second region 20 substantiallysurrounds the first region 18 and extends outwardly therefrom to theouter edges of the substrate 12. In this embodiment, no specificcharacteristic of the substrate itself physically divides the tworegions; however, the regions are demarked for purposes of discussionherein with respect to treatments or features applied thereto orcontained therein.

A microelectronic element 22 can be mounted to first surface 14 ofsubstrate 12 within first region 18. Microelectronic element 22 can be asemiconductor chip or another comparable device. In the embodiment ofFIG. 1, microelectronic element 22 is mounted to first surface 14 inwhat is known as a conventional or “face-up” fashion. In such anembodiment, wire leads 24 can be used to electrically connectmicroelectronic element 22 to some of a plurality of conductive elements28 exposed at first surface 14. Wire leads 24 can also be joined totraces (not shown) or other conductive features within substrate 12 thatare, in turn, connected to conductive elements 28.

Conductive elements 28 include respective “contacts” or pads 30 that areexposed at the first surface 14 of substrate 12. As used in the presentdescription, when an electrically conductive element is described asbeing “exposed at” the surface of another element having dielectricstructure, it indicates that the electrically conductive structure isavailable for contact with a theoretical point moving in a directionperpendicular to the surface of the dielectric structure toward thesurface of the dielectric structure from outside the dielectricstructure. Thus, a terminal or other conductive structure that isexposed at a surface of a dielectric structure may project from suchsurface; may be flush with such surface; or may be recessed relative tosuch surface and exposed through a hole or depression in the dielectric.The conductive elements 28 can be flat, thin elements in which pad 30 isexposed at first surface 14 of substrate 12. In one embodiment,conductive elements 28 can be substantially circular and can beinterconnected between each other or to microelectronic element 22 bytraces (not shown). Conductive elements 28 can be formed at least withinsecond region 20 of substrate 12. Additionally, in certain embodiments,conductive elements 28 can also be formed within first region 18. Suchan arrangement is particularly useful when mounting microelectronicelement 122 (FIG. 3) to substrate 112 in what is known as a “flip-chip”configuration, where contacts on the microelectronic element 122 can beconnected to conductive elements 128 within first region 118 by solderbumps 126 or the like that are positioned beneath microelectronicelement 122. In an embodiment, conductive elements 28 are formed from asolid metal material such as copper, gold, nickel, or other materialsthat are acceptable for such an application, including various alloysincluding one or more of copper, gold, nickel or combinations thereof.

At least some of conductive elements 28 can be interconnected tocorresponding second conductive elements 40, such as conductive pads,exposed at second surface 16 of substrate 12. Such an interconnectioncan be completed using vias 41 formed in substrate 12 that can be linedor filled with conductive metal that can be of the same material asconductive elements 28 and 40. Optionally, conductive elements 40 can befurther interconnected by traces on substrate 12.

Microelectronic assembly 10 further includes a plurality of wire bonds32 joined to at least some of the conductive elements 28, such as on thepads 30 thereof. In some examples, wire bonds 32 may be formed of wire,e.g., of copper or copper alloy, gold, aluminum, or a combination of abase wire metal, e.g., copper, copper alloy, gold or aluminum with ametallic coating finish or layer thereon of a different metal, which insome cases may be gold or palladium. In some cases, the wire may have adiameter ranging from 10 micrometers and up, in more specific examples,can be 17 micrometers, 25 micrometers or greater, e.g., 35 micrometersor 50 micrometers. Where the microelectronic assembly 10 requires alarge number of interconnects, or input or output connections, to themicroelectronic assembly, there may be 1000-2000 wire bonds 32 as anexample.

Wire bonds 32 are bonded along a portion of the edge surface 37 thereofto the conductive elements 28. Examples of such bonding include stitchbonding, wedge bonding and the like. As will be described in furtherdetail below, a wire bonding tool can be used to stitch-bond a segmentof wire extending from a capillary of the wire bonding tool to aconductive element 28 while severing the stitch-bonded end of the wirefrom a supply of wire in the capillary. The wire bonding tool may leavea mark (not shown) near the tip of the wire bonds 32 resulting from aprocess of forming the wire bond. The mark may result in a taperedregion of the wire bond and/or have any geometric shape including aball-shape.

The wire bonds are stitch-bonded to the conductive elements 28 at theirrespective “bases” 34. Hereinafter, the “base” 34 of such stitch-bondedwire bond 32 refers to the portion of the wire bond which forms a jointwith the conductive element 28. Alternatively, wire bonds can be joinedto at least some of the conductive elements using ball bonds, examplesof which are shown and described in co-pending, commonly assigned U.S.patent application, the entire disclosure of which is incorporated byreference herein.

The incorporation of various forms of edge bonds, as described herein,can allow for conductive elements 28 to be non-solder-mask-defined(“NSMD”) type conductive elements. In packages using other types ofconnections to conductive elements, for example solder balls or thelike, the conductive elements are solder-mask defined. That is theconductive elements are exposed in openings formed in a solder maskmaterial layer. In such an arrangement, the solder mask layer canpartially overlie the conductive elements or can contact the conductiveelements along an edge thereof. By contrast, a NSMD conductive elementis one that is not contacted by a solder mask layer. For example, theconductive element can be exposed on a surface of a substrate that doesnot have a solder mask layer or, if present, a solder mask layer on thesurface can have an opening with edges spaced away from the conductiveelement. Such NSMD conductive elements can also be formed in shapes thatare not round. Solder-mask defined pads can often be round when intendedto be used to bond to an element via a solder mass, which forms agenerally round profile on such a surface. When using, for example, anedge bond to attach to a conductive element, the bond profile itself isnot round, which can allow for a non-round conductive element. Suchnon-round conductive elements can be, for example oval, rectangular, orof a rectangular shape with rounded corners. They can further beconfigured to be longer in the direction of the edge bond to accommodatethe bond, while being shorter in the direction of the wire bond's 32width. This can allow for a finer pitch at the substrate 12 level. Inone example, the conductive elements 28 can be between about 10% and 25%larger than the intended size of base 34 in both directions. This canallow for variations in the precision with which the bases 34 arelocated and for variations in the bonding process.

In some embodiments, an edge bonded wire bond, as described above, whichcan be in the form of a stitch bond, can be combined with a ball bond.As shown in FIG. 23A a ball bond 1333 can be formed on a conductiveelement 1328 and a wire bond 1332 can be formed with a base 1338 stitchbonded along a portion of the edge surface 1337 to ball bond 1372. Inanother example, the general size and placement of the ball bond can beas shown at 1372′. In another variation shown in FIG. 23B, a wire bond1332 can be edge bonded along conductive element 1328, such as by stitchbonding, as described above. A ball bond 1373 can then be formed on topof the base 1338 of wire bond 1334. In one example, the size andplacement of the ball bond can be as shown at 1373′. Each of the wirebonds 32 can extend to a free end 36 remote from the base 34 of suchwire bond and remote from substrate 12. The ends 36 of wire bonds 32 arecharacterized as being free in that they are not electrically connectedor otherwise joined to microelectronic element 22 or any otherconductive features within microelectronic assembly 10 that are, inturn, connected to microelectronic element 22. In other words, free ends36 are available for electronic connection, either directly orindirectly as through a solder ball or other features discussed herein,to a conductive feature external to assembly 10. The fact that ends 36are held in a predetermined position by, for example, encapsulationlayer 42 or otherwise joined or electrically connected to anotherconductive feature does not mean that they are not “free” as describedherein, so long as any such feature is not electrically connected tomicroelectronic element 22. Conversely, base 34 is not free as it iseither directly or indirectly electrically connected to microelectronicelement 22, as described herein. As shown in FIG. 1, the bases 34 of thewire bonds 32 typically are curved at their stitch-bond (or otheredge-bonded) joints with the respective conductive elements 28. Eachwire bond has an edge surface 37 extending between the base 34 thereofand the end 36 of such wire bond. The particular size and shape of base34 can vary according to the type of material used to form wire bond 32,the desired strength of the connection between wire bond 32 andconductive element 28, or the particular process used to form wire bond32. Alternative embodiments are possible where wire bonds 32 areadditionally or alternatively joined to conductive elements 40 exposedon second surface 16 of substrate 12, extending away therefrom.

In a particular example, a first one of the wire bonds 32 may beadapted, i.e., constructed, arranged, or electrically coupled to othercircuitry on the substrate for carrying a first signal electricpotential, and a second one of the wire bonds 32 may be so adapted forsimultaneously carrying a second signal electric potential differentfrom the first signal electric potential. Thus, when a microelectronicpackage as seen in FIGS. 1 and 2 is energized, the first and second wirebonds can simultaneously carry first and second different signalelectric potentials.

Wire bond 32 can be made from a conductive material such as copper,copper alloy or gold. Additionally, wire bonds 32 can be made fromcombinations of materials, such as from a core of a conductive material,such as copper or aluminum, for example, with a coating applied over thecore. The coating can be of a second conductive material, such asaluminum, nickel or the like. Alternatively, the coating can be of aninsulating material, such as an insulating jacket.

In particular embodiments, the wire bonds may have a core of primarymetal and a metallic finish including a second metal different from theprimary metal overlying the primary metal. For example, the wire bondsmay have a primary metal core of copper, copper alloy, aluminum or goldand the metallic finish can include palladium. Palladium can avoidoxidation of a core metal such as copper, and may serve as a diffusionbarrier to avoid diffusion a solder-soluble metal such as gold in solderjoints between unencapsulated portions of the wire bonds and anothercomponent as will be described further below. Thus, in one embodiment,the wire bonds can be formed of palladium-coated copper wire orpalladium-coated gold wire which can be fed through the capillary of thewire bonding tool.

In an embodiment, the wire used to form wire bonds 32 can have athickness, i.e., in a dimension transverse to the wire's length, ofbetween about 15 μm and 150 μm. In general, a wire bond is formed on aconductive element, such as conductive element 28, a pad, trace or thelike, using specialized equipment that is known in the art. The free end36 of wire bond 32 has an end surface 38. End surface 38 can form atleast a part of a contact in an array formed by respective end surfaces38 of a plurality of wire bonds 32. FIG. 2 shows an exemplary patternfor such an array of contacts formed by end surfaces 38. Such an arraycan be formed in an area array configuration, variations of which couldbe implemented using the structures described herein. Such an array canbe used to electrically and mechanically connect the microelectronicassembly 10 to another microelectronic structure, such as to a printedcircuit board (“PCB”), or to other packaged microelectronic elements, anexample of which is shown in FIG. 6. In such a stacked arrangement, wirebonds 32 and conductive elements 28 and 40 can carry multiple electronicsignals therethrough, each having a different signal potential to allowfor different signals to be processed by different microelectronicelements in a single stack. Solder masses 52 can be used to interconnectthe microelectronic assemblies in such a stack, such as byelectronically and mechanically attaching end surfaces 38 to conductiveelements 40.

Microelectronic assembly 10 further includes an encapsulation layer 42formed from a dielectric material. In the embodiment of FIG. 1,encapsulation layer 42 is formed over the portions of first surface 14of substrate 12 that are not otherwise covered by or occupied bymicroelectronic element 22, or conductive elements 28. Similarly,encapsulation layer 42 is formed over the portions of conductiveelements 28, including pad 30 thereof, that are not otherwise covered bywire bonds 32. Encapsulation layer 42 can also substantially covermicroelectronic element 22, wire bonds 32, including the bases 34 and atleast a portion of edge surfaces 37 thereof. A portion of wire bonds 32can remain uncovered by encapsulation layer 42, which can also bereferred to as unencapsulated portions 39, thereby making the wire bondavailable for electrical connection to a feature or element locatedoutside of encapsulation layer 42. In an embodiment, end surfaces 38 ofwire bonds 32 remain uncovered by encapsulation layer 42 within majorsurface 44 of encapsulation layer 42. Other embodiments are possible inwhich a portion of edge surface 37 is uncovered by encapsulation layer42 in addition to or as an alternative to having end surface 38 remainuncovered by encapsulation layer 42. In other words, encapsulation layer42 can cover all of microelectronic assembly 10 from first surface 14and above, with the exception of a portion of wire bonds 36, such as endsurfaces 38, edge surfaces 37 or combinations of the two. In theembodiments shown in the Figures, a surface, such as major surface 44 ofencapsulation layer 42 can be spaced apart from first surface 14 ofsubstrate 12 at a distance great enough to cover microelectronic element22. Accordingly, embodiments of microelectronic assembly 10 in whichends 38 of wire bonds 32 are flush with surface 44, will include wirebonds 32 that are taller than the microelectronic element 22, and anyunderlying solder bumps for flip chip connection. Other configurationsfor encapsulation layer 42, however, are possible. For example, theencapsulation layer can have multiple surfaces with varying heights. Insuch a configuration, the surface 44 within which ends 38 are positionedcan be higher or lower than an upwardly facing surface under whichmicroelectronic element 22 is located.

Encapsulation layer 42 serves to protect the other elements withinmicroelectronic assembly 10, particularly wire bonds 32. This allows fora more robust structure that is less likely to be damaged by testingthereof or during transportation or assembly to other microelectronicstructures. Encapsulation layer 42 can be formed from a dielectricmaterial with insulating properties such as that described in U.S.Patent App. Pub. No. 2010/0232129, which is incorporated by referenceherein.

FIG. 3 shows an embodiment of microelectronic assembly 110 having wirebonds 132 with ends 136 that are not positioned directly above therespective bases 34 thereof. That is, considering first surface 114 ofsubstrate 112 as extending in two lateral directions, so as tosubstantially define a plane, end 136 or at least one of the wire bonds132 is displaced in at least one of these lateral directions from acorresponding lateral position of base 134. As shown in FIG. 3, wirebonds 132 can be substantially straight along the longitudinal axisthereof, as in the embodiment of FIG. 1, with the longitudinal axisbeing angled at an angle 146 with respect to first surface 114 ofsubstrate 112. Although the cross-sectional view of FIG. 3 only showsthe angle 146 through a first plane perpendicular to first surface 114,wire bond 132 can also be angled with respect to first surface 114 inanother plane perpendicular to both that first plane and to firstsurface 114. Such an angle can be substantially equal to or differentthan angle 146. That is the displacement of end 136 relative to base 134can be in two lateral directions and can be by the same or a differentdistance in each of those directions.

In an embodiment, various ones of wire bonds 132 can be displaced indifferent directions and by different amounts throughout the assembly110. Such an arrangement allows for assembly 110 to have an array thatis configured differently on the level of surface 144 compared to on thelevel of substrate 12. For example, an array can cover a smaller overallarea or have a smaller pitch on surface 144 compared to that at firstsurface 114 of substrate 112. Further, some wire bonds 132 can have ends138 that are positioned above microelectronic element 122 to accommodatea stacked arrangement of packaged microelectronic elements of differentsizes. In another example, wire bonds 132 can be configured such thatthe end of one wire bond is positioned substantially above the base of asecond wire bond, wherein the end of that second wire bond beingpositioned elsewhere. Such an arrangement can be referred to as changingthe relative position of a contact end surface 136 within an array ofcontacts, compared to the position of a corresponding contact array onsecond surface 116. In another example, shown in FIG. 8, wire bonds 132can be configured such that the end 136A of one wire bond 132A ispositioned substantially above the base 134B of another wire bond 134B,the end 132B of that wire bond 134B being positioned elsewhere. Such anarrangement can be referred to as changing the relative position of acontact end surface 136 within an array of contacts, compared to theposition of a corresponding contact array on second surface 116. Withinsuch an array, the relative positions of the contact end surfaces can bechanged or varied, as desired, depending on the microelectronicassembly's application or other requirements. FIG. 4 shows a furtherembodiment of a microelectronic subassembly 210 having wire bonds 232with ends 236 in displaced lateral positions with respect to bases 234.In the embodiment of FIG. 4, the wire bonds 132 achieve this lateraldisplacement by including a curved portion 248 therein. Curved portion248 can be formed in an additional step during the wire bond formationprocess and can occur, for example, while the wire portion is beingdrawn out to the desired length. This step can be carried out usingavailable wire-bonding equipment, which can include the use of a singlemachine.

Curved portion 248 can take on a variety of shapes, as needed, toachieve the desired positions of the ends 236 of the wire bonds 232. Forexample, curved portions 248 can be formed as S-curves of variousshapes, such as that which is shown in FIG. 4 or of a smoother form(such as that which is shown in FIG. 5). Additionally, curved portion248 can be positioned closer to base 234 than to end 236 or vice-versa.Curved portion 248 can also be in the form of a spiral or loop, or canbe compound including curves in multiple directions or of differentshapes or characters.

In a further example shown in FIG. 26, the wire bonds 132 can bearranged such that the bases 134 are arranged in a first pattern havinga pitch thereof. The wire bonds 132 can be configured such that theunencapsulated portions thereof 139 including end surfaces 138, can bedisposed at positions in a pattern having a minimum pitch betweenadjacent unencapsulated portions 38 of the wire bonds 32 exposed at thesurface 44 of the encapsulation layer that is greater than the minimumpitch between adjacent bases of the plurality of bases 134 and,accordingly, the conductive elements 128 to which the bases are joined).To achieve this, the wire bonds can include portions which extend in oneor more angles relative to a normal direction to the conductiveelements, such as shown in FIG. 26. In another example, the wire bondscan be curved as shown, for example in FIG. 4, such that the ends 238are displaced in one or more lateral directions from the bases 134, asdiscussed above. As further shown in FIG. 26, the conductive elements128 and the ends 138 can be arranged in respective rows or columns andthe lateral displacement of end surfaces 138 at some locations, such asin one row of the ends, from the respective conductive elements on thesubstrate to which they are joined can be greater than the lateraldisplacement of the unencapsulated portions at other locations from therespective conductive elements to which they are connected. To achievethis, the wire bonds 132 can, for example be at different angles 146A,146B with respect to the surface 116 of the substrate 112.

FIG. 5A shows a further exemplary embodiment of a microelectronicpackage 310 having a combination of wire bonds 332 having various shapesleading to various relative lateral displacements between bases 334 andends 336. Some of wire bonds 332A are substantially straight with ends336A positioned above their respective bases 334A, while other wirebonds 332B include a subtle curved portion 348B leading to a somewhatslight relative lateral displacement between end 336B and base 334B.Further, some wire bonds 332C include curved portions 348C having asweeping shape that result in ends 336C that are laterally displacedfrom the relative bases 334C at a greater distance than that of ends334B. FIG. 5 also shows an exemplary pair of such wire bonds 332Ci and332Cii that have bases 334Ci and 334Cii positioned in the same row of asubstrate-level array and ends 336Ci and 336Cii that are positioned indifferent rows of a corresponding surface-level array. In some cases,the radius of bends in the wire bonds 332Ci, 332Cii can be large suchthat the curves in the wire bonds may appear continuous. In other cases,the radius of the bends may be relatively small, and the wire bonds mayeven have straight portions or relatively straight portions betweenbends in the wire bonds. Moreover, in some cases the unencapsulatedportions of the wire bonds can be displaced from their bases by at leastone minimum pitch between the contacts 328 of the substrate. In othercases, the unencapsulated portions of the wire bonds can be displacedfrom their bases by at least 200 micrometers.

A further variation of a wire bond 332D is shown that is configured tobe uncovered by encapsulation layer 342 on a side surface 47 thereof. Inthe embodiment shown free end 336D is uncovered, however, a portion ofedge surface 337D can additionally or alternatively be uncovered byencapsulation layer 342. Such a configuration can be used for groundingof microelectronic assembly 10 by electrical connection to anappropriate feature or for mechanical or electrical connection to otherfeatured disposed laterally to microelectronic assembly 310.Additionally, FIG. 5 shows an area of encapsulation layer 342 that hasbeen etched away, molded, or otherwise formed to define a recessedsurface 345 that is positioned closer to substrate 12 than major surface342. One or more wire bonds, such as wire bond 332A can be uncoveredwithin an area along recessed surface 345. In the exemplary embodimentshown in FIG. 5, end surface 338A and a portion of edge surface 337A areuncovered by encapsulation layer 342. Such a configuration can provide aconnection, such as by a solder ball or the like, to another conductiveelement by allowing the solder to wick along edge surface 337A and jointhereto in addition to joining to end surface 338. Other configurationsby which a portion of a wire bond can be uncovered by encapsulationlayer 342 along recessed surface 345 are possible, including ones inwhich the end surfaces are substantially flush with recessed surface 345or other configurations shown herein with respect to any other surfacesof encapsulation layer 342.

Similarly, other configurations by which a portion of wire bond 332D isuncovered by encapsulation layer 342 alongside surface 347 can besimilar to those discussed elsewhere herein with respect to thevariations of the major surface of the encapsulation layer.

FIG. 5A further shows a microelectronic assembly 310 having twomicroelectronic elements 322 and 350 in an exemplary arrangement wheremicroelectronic element 350 is stacked, face-up, on microelectronicelement 322. In this arrangement, leads 324 are used to electricallyconnect microelectronic element 322 to conductive features on substrate312. Various leads are used to electronically connect microelectronicelement 350 to various other features of microelectronic assembly 310.For example, lead 380 electrically connects microelectronic element 350to conductive features of substrate 312, and lead 382 electricallyconnects microelectronic element 350 to microelectronic element 322.Further, wire bond 384, which can be similar in structure to variousones of wire bonds 332, is used to form a contact surface 386 on thesurface 344 of encapsulation layer 342 that electrically connected tomicroelectronic element 350. This can be used to directly electricallyconnect a feature of another microelectronic assembly to microelectronicelement 350 from above encapsulation layer 342. Such a lead could alsobe included that is connected to microelectronic element 322, includingwhen such a microelectronic element is present without a secondmicroelectronic element 350 affixed thereon. An opening (not shown) canbe formed in encapsulation layer 342 that extends from surface 344thereof to a point along, for example, lead 380, thereby providingaccess to lead 380 for electrical connection thereto by an elementlocated outside surface 344. A similar opening can be formed over any ofthe other leads or wire bonds 332, such as over wire bonds 332C at apoint away from the ends 336C thereof. In such an embodiment, ends 336Ccan be positioned beneath surface 344, with the opening providing theonly access for electrical connection thereto.

Additional arrangements for microelectronic packages having multiplemicroelectronic elements are shown in FIGS. 27A-C. These arrangementscan be used in connection with the wire bond arrangements shown, forexample in FIG. 5A and in the stacked package arrangement of FIG. 6,discussed further below. Specifically, FIG. 27A shows an arrangement inwhich a lower microelectronic element 1622 is flip-chip bonded toconductive elements 1628 on the surface 1614 of substrate 1612. Thesecond microelectronic element 1650 can overlie the firstmicroelectronic element 1622 and be face-up connected to additionalconductive elements 1628 on the substrate, such as through wire bonds1688. FIG. 27B shows an arrangement where a first microelectronicelement 1722 is face-up mounted on surface 1714 and connected throughwire bonds 1788 to conductive elements 1728. Second microelectronicelement 1750 can have contacts exposed at a face thereof which face andare joined to corresponding contacts at a face of the firstmicroelectronic element 1722 which faces away from the substrate througha set of contacts 1726 of the second microelectronic element 1750 whichface and are joined to corresponding contacts on the front face of thefirst microelectronic element 1722. These contacts of the firstmicroelectronic element 1722 which are joined to corresponding contactsof the second microelectronic element can in turn be connected throughcircuit patterns of the first microelectronic element 1722 and beconnected by ire bonds 1788 to the conductive elements 1728 on substrate1712.

FIG. 27C shows an example in which first and second microelectronicelements 1822, 1850 are spaced apart from one another in a directionalong a surface 1814 of substrate 1812. Either one or both of themicroelectronic elements (and additional microelectronic elements) canbe mounted in face-up or flip-chip configurations described herein.Further, any of the microelectronic elements employed in such anarrangement can be connected to each other through circuit patterns onone or both such microelectronic elements or on the substrate or onboth, which electrically connect respective conductive elements 1828 towhich the microelectronic elements are electrically connected.

FIG. 5B further illustrates a structure according to a variation of theabove-described embodiments in which a second conductive element 43 canbe formed in contact with an unencapsulated portion 39 of a wire bondexposed at or projecting above a surface 44 of the encapsulation layer42, the second conductive element not contacting the first conductiveelement 28 (FIG. 1). In one embodiment as seen in FIG. 5B, the secondconductive element can include a pad 45 extending onto a surface 44 ofthe encapsulation layer which can provide a surface for joining with abonding metal or bonding material of a component thereto.

Alternatively, as seen in FIG. 5C, the second conductive element 48 canbe a metallic finish selectively formed on the unencapsulated portion 39of a wire bond. In either case, in one example, the second conductiveelement 43 or 48 can be formed, such as by plating, of a layer of nickelcontacting the unencapsulated portion of the wire bond and overlying acore of the wire bond, and a layer of gold or silver overlying the layerof nickel. In another example, the second conductive element may be amonolithic metal layer consisting essentially of a single metal. In oneexample, the single metal layer can be nickel, gold, copper, palladiumor silver. In another example, the second conductive element 43 or 48can include or be formed of a conductive paste contacting theunencapsulated portion 39 of the wire bond. For example, stenciling,dispensing, screen printing, controlled spraying, e.g., a processsimilar to inkjet printing, or transfer molding can be used to formsecond conductive elements 43 or 48 on the unencapsulated portions 39 ofthe wire bonds.

FIG. 5D further illustrates a second conductive element 43D which can beformed of a metal or other electrically conductive material as describedfor conductive elements 43, 48 above, wherein the second conductiveelement 43D is formed at least partly within an opening 49 extendinginto an exterior surface 44 of the encapsulation layer 42. In oneexample, the opening 49 can be formed by removing a portion of theencapsulation layer after curing or partially curing the encapsulationlayer so as to simultaneously expose a portion of the wire bondthereunder which then becomes the unencapsulated portion of the wirebond. For example, the opening 49 can be formed by laser ablation,etching. In another example, a soluble material can be pre-placed at thelocation of the opening prior to forming the encapsulation layer and thepre-placed material then can be removed after forming the encapsulationlayer to form the opening.

In a further example, as seen in FIGS. 24A-24B, multiple wire bonds 1432can have bases joined with a single conductive element 1428. Such agroup of wire bonds 1432 can be used to make additional connectionpoints over the encapsulation layer 1442 for electrical connection withconductive element 1428. The exposed portions 1439 of thecommonly-joined wire bonds 1432 can be grouped together on surface 1444of encapsulation layer 1442 in an area, for example about the size ofconductive element 1428 itself or another area approximating theintended size of a bonding mass for making an external connection withthe wire bond 1432 group. As shown, such wire bonds 1432 can be eitherball-bonded (FIG. 24A) or edge bonded (FIG. 24B) on conductive element1428, as described above, or can be bonded to the conductive element asdescribed above with respect to FIG. 23A or 23B or both.

As shown in FIGS. 25A and 25B, ball-bonded wire bonds 1532 can be formedas stud bumps on at least some of the conductive elements 1528. Asdescribed herein a stud bump is a ball-bonded wire bond where thesegment of wire extending between the base 1534 and the end surface 1538has a length of at most 300% of the diameter of the ball-bonded base1534. As in other embodiments, the end surface 1538 and optionally aportion of the edge surface 1537 of the stud bump can be unencapsulatedby the encapsulation layer 1542. As shown in FIG. 25B such a stud bump1532A can be formed on top of another stud bump 1532B to form,essentially, a base 1534 of a wire bond 1532 made up of the two ballbonds with a wire segment extending therefrom up to the surface 1544 ofthe encapsulation layer 1542. Such wire bonds 1532 can have a heightthat is less than, for example, the wire bonds described elsewhere inthe present disclosure. Accordingly, the encapsulation layer can includea major surface 1544 in an area, for example overlying themicroelectronic element 1522 and a minor surface 1545 spaced above thesurface 1514 of the substrate 1512 at a height less than that of themajor surface 1544. Such arrangements can also be used to form alignmentfeatures and to reduce the overall height of a package employing studbump type wire bonds as well as other types of wire bonds disclosedherein, while accommodating conductive masses 1552 that can connect theunencapsulated portions 1539 of the wire bonds 1532 with contacts 1543on another microelectronic package 1588.

FIG. 6 shows a stacked package of microelectronic assemblies 410 and488. In such an arrangement solder masses 452 electrically andmechanically connect end surfaces 438 of assembly 410 to conductiveelements 440 of assembly 488. The stacked package can include additionalassemblies and can be ultimately attached to contacts 492 on a PCB 490or the like for use in an electronic device. In such a stackedarrangement, wire bonds 432 and conductive elements 430 can carrymultiple electronic signals therethrough, each having a different signalpotential to allow for different signals to be processed by differentmicroelectronic elements, such as microelectronic element 422 ormicroelectronic element 489, in a single stack.

In the exemplary configuration in FIG. 6, wire bonds 432 are configuredwith a curved portion 448 such that at least some of the ends 436 of thewire bonds 432 extend into an area that overlies a major surface 424 ofthe microelectronic element 422. Such an area can be defined by theouter periphery of microelectronic element 422 and extending upwardlytherefrom. An example of such a configuration is shown from a viewfacing toward first surface 414 of substrate 412 in FIG. 18, where wirebonds 432 overlie a rear major surface of the microelectronic element422, which is flip-chip bonded at a front face 425 thereof to substrate412. In another configuration (FIG. 5), the microelectronic element 422can be mounted face-up to the substrate 312, with the front face 325facing away from the substrate 312 and at least one wire bond 336overlying the front face of microelectronic element 322. In oneembodiment, such wire bond 336 is not electrically connected withmicroelectronic element 322. A wire bond 336 bonded to substrate 312 mayalso overlie the front or rear face of microelectronic element 350. Theembodiment of microelectronic assembly 410 shown in FIG. 7 is such thatconductive elements 428 are arranged in a pattern forming a first arrayin which the conductive elements 428 are arranged in rows and columnssurrounding microelectronic element 422 and may have a predeterminedpitch between individual conductive elements 428. Wire bonds 432 arejoined to the conductive elements 428 such that the respective bases 434thereof follow the pattern of the first array as set out by theconductive elements 428. Wire bonds 432 are configured, however, suchthat the respective ends 436 thereof can be arranged in a differentpattern according to a second array configuration. In the embodimentshown the pitch of the second array can be different from, and in somecases finer than that of the first array. However, other embodiments arepossible in which the pitch of the second array is greater than thefirst array, or in which the conductive elements 428 are not positionedin a predetermined array but the ends 436 of the wire bonds 432 are.Further still, conductive elements 428 can be configured in sets ofarrays positioned throughout substrate 412 and wire bonds 432 can beconfigured such that ends 436 are in different sets of arrays or in asingle array.

FIG. 6 further shows an insulating layer 421 extending along a surfaceof microelectronic element 422. Insulating layer 421 can be formed froma dielectric or other electrically insulating material prior to formingthe wire bonds. The insulating layer 421 can protect microelectronicelement from coming into contact with any of wire bonds 423 that extendthereover. In particular, insulating layer 421 can avoid electricalshort-circuiting between wire bonds and short-circuiting between a wirebond and the microelectronic element 422. In this way, the insulatinglayer 421 can help avoid malfunction or possible damage due tounintended electrical contact between a wire bond 432 and themicroelectronic element 422.

The wire bond configuration shown in FIGS. 6 and 7 can allow formicroelectronic assembly 410 to connect to another microelectronicassembly, such as microelectronic assembly 488, in certain instanceswhere the relative sizes of, for example, microelectronic assembly 488and microelectronic element 422 would not otherwise permit. In theembodiment of FIG. 6 microelectronic assembly 488 is sized such thatsome of the contact pads 440 are in an array within an area smaller thanthe area of the front or rear surface 424 or 426 of the microelectronicelement 422. In a microelectronic assembly having substantially verticalconductive features, such as pillars, in place of wire bonds 432, directconnection between conductive elements 428 and pads 440 would not bepossible. However, as shown in FIG. 6, wire bonds 432 havingappropriately-configured curved portions 448 can have ends 436 in theappropriate positions to make the necessary electronic connectionsbetween microelectronic assembly 410 and microelectronic assembly 488.Such an arrangement can be used to make a stacked package wheremicroelectronic assembly 418 is, for example, a DRAM chip or the likehaving a predetermined pad array, and wherein microelectronic element422 is a logic chip configured to control the DRAM chip. This can allowa single type of DRAM chip to be used with several different logic chipsof varying sizes, including those which are larger than the DRAM chipbecause the wire bonds 432 can have ends 436 positioned wherevernecessary to make the desired connections with the DRAM chip. In analternative embodiment, microelectronic package 410 can be mounted onprinted circuit board 490 in another configuration, where theunencapsulated surfaces 436 of wire bonds 432 are electrically connectedto pads 492 of circuit board 490. Further, in such an embodiment,another microelectronic package, such as a modified version of package488 can be mounted on package 410 by solder balls 452 joined to pads440.

FIGS. 9 and 10 show a further embodiment of a microelectronic assembly510 in which wire bonds 532 are formed on a lead-frame structure.Examples of lead frame structures are shown and described in U.S. Pat.Nos. 7,176,506 and 6,765,287 the disclosures of which are herebyincorporated by reference herein. In general, a lead frame is astructure formed from a sheet of conductive metal, such as copper, thatis patterned into segments including a plurality of leads and canfurther include a paddle, and a frame. The frame is used to secure theleads and the paddle, if used, during fabrication of the assembly. In anembodiment, a microelectronic element, such as a die or chip, can bejoined face-up to the paddle and electrically connected to the leadsusing wire bonds. Alternatively, the microelectronic element can bemounted directly onto the leads, which can extend under themicroelectronic element. In such an embodiment, contacts on themicroelectronic element can be electrically connected to respectiveleads by solder balls or the like. The leads can then be used to formelectrical connections to various other conductive structures forcarrying an electronic signal potential to and from the microelectronicelement. When the assembly of the structure is complete, which caninclude forming an encapsulation layer thereover, temporary elements ofthe frame can be removed from the leads and paddle of the lead frame, soas to form individual leads. For purposes of this disclosure, theindividual leads 513 and the paddle 515 are considered to be segmentedportions of what, collectively, forms a substrate 512 that includesconductive elements 528 in portions that are integrally formedtherewith. Further, in this embodiment, paddle 515 is considered to bewithin first region 518 of substrate 512, and leads 513 are consideredto be within second region 520. Wire bonds 524, which are also shown inthe elevation view of FIG. 10, connect microelectronic element 22, whichis carried on paddle 515, to conductive elements 528 of leads 515. Wirebonds 532 can be further joined at bases 534 thereof to additionalconductive elements 528 on leads 515. Encapsulation layer 542 is formedonto assembly 510 leaving ends 538 of wire bonds 532 uncovered atlocations within surface 544. Wire bonds 532 can have additional oralternative portions thereof uncovered by encapsulation layer 542 instructures that correspond to those described with respect to the otherembodiments herein.

FIG. 11 further illustrates use of an underfill 620 for mechanicallyreinforcing the joints between wire bonds 632 of one package 610A andsolder masses 652 of another package 610B mounted thereon. As shown inFIG. 11, although the underfill 620 need only be disposed betweenconfronting surfaces 642, 644 of the packages 610A, 610B, the underfill620 can contact edge surfaces of package 610A and may contact a firstsurface 692 of the circuit panel 690 to which the package 610 ismounted. Further, portions of the underfill 620 that extend along theedge surfaces of the packages 610A, 610B, if any, can be disposed at anangle between 0° and 90° relative to a major surface of the circuitpanel over which the packages are disposed, and can be tapered from agreater thickness adjacent the circuit panel to a smaller thickness at aheight above the circuit panel and adjacent one or more of the packages.

A package arrangement shown in FIGS. 28A-D can be implemented in onetechnique for making an underfill layer, and in particular a portionthereof that is disposed between confronting faces of packages 1910A and1910B, such as surface 1942 of package 1910A and surface 1916 of package1910B. As shown in FIG. 28A, package 1910A can extend beyond an edgesurface 1947 of package 1910B such that, for example, the surface 1944of encapsulation layer 1942 has a portion thereof that is exposedoutside of package 1910B. Such an area can be used as a dispensing area1949 whereby a device can deposit an underfill material in a flowablestate on the dispensing area from a vertical position relative thereto.In such an arrangement, the dispensing area 1949 can be sized such thatthe underfill material can be deposited in a mass on the surface withoutspilling off of the edge of the surface while reaching a sufficientvolume to flow under package 1910B where it can be drawn by capillaryinto the area between the confronting surfaces of packages 1910A and1910B, including around any joints therebetween, such as solder massesor the like. As the underfill material is drawn between confrontingsurfaces, additional material can be deposited on the dispensing areasuch that a continuous flow is achieved that does not significantlyspill over the edge of package 1910A. As shown in FIG. 28B, thedispensing area 1949 can surround package 1910B and have a dimension Din an orthogonal direction away from a peripheral edge of package 1910Bof about one millimeter (1 mm) on each side thereof. Such an arrangementcan allow for dispensing on one side of package 1910B or more than oneside, either sequentially or simultaneously. Alternative arrangementsare shown in FIG. 28C, wherein the dispensing area 1949 extends alongonly two adjacent sides of package 1910B and have a dimension D′ ofabout 1 mm in a direction orthogonally away from a peripheral edge ofthe second package, and FIG. 28D, wherein the dispensing area 1949extends along a single side of package 1910B and may have a dimension D″in an orthogonal direction away from the peripheral edge of the packageof, for example 1.5 mm to 2 mm.

In an arrangement where microelectronic packages 2010A and 2010B are ofsimilar sizes in a horizontal profile, a compliant bezel 2099 can beused to secure the packages 2010A and 2010B together during attachmentby, for example, joining of terminals of the second package with theelements comprising the unencapsulated portions 2039 of the wire bonds2032, e.g., by heating or curing of conductive masses 2052, e.g.,reflowing of solder masses, to join the packages 2010A and 2010Btogether. Such an arrangement is shown in FIG. 29 in which package 2010Bis assembled over package 2010A with conductive masses 2052, e.g.,solder masses, for example, joined to terminals 2043 on package 2010B.The packages can be aligned so that the solder masses 2052 align withunencapsulated portions 2039 of the wire bonds 2032 of package 2010A orwith second conductive elements joined with the end surfaces 2038 of thewire bonds 2032, as described above. The bezel 2099 can then beassembled around packages 2010A and 2010B to maintain such alignmentduring a heating process in which the terminals of the second packageare joined with the wire bonds 2032 or second conductive elements of thefirst package. For example, a heating process can be used to reflowsolder masses 2052 to bond the terminals of the second package with thewire bonds 2032 or second conductive elements. Bezel 2099 can alsoextend inward along portions of surface 2044 of package 2010B and alongsurface 2016 of package 2010A to maintain the contact between thepackages before and during reflow. The bezel 2099 can be of aresiliently compliant material such as rubber, TPE, PTFE(polytetrafluoroethylene), silicone or the like and can be undersizedrelative to the size of the assembled packages such that a compressiveforce is applied by the bezel when in place. The bezel 2099 can also beleft in place during the application of an underfill material and caninclude an opening to accommodate such application therethrough. Thecompliant bezel 2099 can be removed after package assembly.

Additionally or alternatively, the assembly of microelectronic packages2110A and 2110B, as shown in FIGS. 30A-F, a lower package 2110A caninclude at least one alignment surface 2151. One example of this isshown in FIG. 30A in which alignment surfaces 2151 are included inencapsulation layer 2142 near the corners of the package 2110B. Thealignment surfaces are sloped relative to the major surface and definean angle of between about 0° and up to and including 90° relative tomajor surface 2144 at some location therefrom, the alignment surfacesextending locations proximate the major surface 2144 and respectiveminor surfaces 2145 that are spaced above substrate 2112 at a greaterdistance than major surface 2144. The minor surfaces 2145 can bedisposed adjacent the corners of package 2110A and can extend partiallybetween intersecting sides thereof. As shown in FIG. 30B, the alignmentsurfaces can also form inside corners opposite the intersecting sides ofthe package 2110A and can be included in similar form along all corners,for example four corners, of package 2110A. As illustrated in FIG. 30C,the alignment surfaces 2151 can be positioned at an appropriate distancefrom unencapsulated portions of corresponding wire bonds 2132 such thatwhen a second package 2110B having protrusions, e.g., electricallyconductive protrusions such as conductive masses or solder balls joinedthereto is stacked on top of package 2110A, the alignment surfaces 2151will guide the solder balls into the proper position overlying theunencapsulated portions of the wire bonds 2132 that correspond with thealignment surfaces 2151. The solder balls can then be reflowed to joinwith the unencapsulated portions of the wire bonds 2132 of package2110A.

A further arrangement employing alignment surfaces 2251 is shown inFIGS. 31A-C, wherein the alignment surfaces 2251 extend between a raisedinner surface 2244 to a lower outer surface 2245. In such anarrangement, inner surface 2244 can overlie microelectronic element 2222and can be spaced above substrate 2212 accordingly. Outer surface 2245can be spaced closer to substrate 2212 in a direction of the thicknessof the substrate and can be positioned vertically between surface 2214of substrate 2212 and surface 2223 of microelectronic element 2222. Oneor more unencapsulated portions of wire bonds 2232 can be positionedrelative to the alignment surfaces 2251 to achieve alignment of solderballs 2252 or other conductive protrusion as described with respect toFIGS. 30A-C. As described above, such a stepped arrangement can be usedwith or without the described alignment functionality to achieve anoverall lower assembly height given a certain bond mass size. Further,the incorporation of a raised inner surface 2244 can lead to increasedresistance of package 2210A to warping.

FIG. 12 is a photographic image showing exemplary joints between thewire bonds 632 of a first component 610A and corresponding solder masses652 of a second component such as a microelectronic package 610B. InFIG. 12, reference 620 indicates where an underfill can be disposed.

FIGS. 13A, 13B, 13C, 13D, 13E and 13F illustrate some possiblevariations in the structure of the wire bonds 32 as described aboverelative to FIG. 1. For example, as seen in FIG. 13A, a wire bond 732Amay have an upwardly extending portion 736 which terminates in an end738A having the same radius as the radius of portion 736.

FIG. 13B illustrates a variation in which the ends 738B are tips whichare tapered relative to portion 736. In addition, as seen in FIG. 13C, atapered tip 738B of a wire bond 732A may have a centroid 740 which isoffset in a radial direction 741 from an axis of a cylindrical portionof the wire bond integral therewith. Such shape may be a bonding toolmark resulting from a process of forming the wire bond as will bedescribed further below. Alternatively, a bonding tool mark other thanas shown at 738B may be present on the unencapsulated portion of thewire bond. As further seen in FIG. 13A, the unencapsulated portion 739of a wire bond may project away from the substrate 712 at an angle 750within 25 degrees of perpendicular to the surface 730 of the substrateon which the conductive elements 728 are disposed.

FIG. 13D illustrates that an unencapsulated portion of a wire bond 732Dcan include a ball-shaped portion 738D. Some of all of the wire bonds onthe package can have such structure. As seen in FIG. 13D, theball-shaped portion 738D can be integral with a cylindrical portion 736of the wire bond 732D, wherein the ball-shaped portion and at least acore of the cylindrical portion of the wire bond consist essentially ofcopper, copper alloy or gold. As will be described further below, theball-shaped portion can be formed by melting a portion of the wireexposed at an opening of the capillary of the bonding tool during apre-shaping process before stitch-bonding the wire bond to a conductiveelement 728 of the substrate. As seen in FIG. 13D, the diameter 744 ofthe ball-shaped portion 738D may be greater than the diameter 746 of thecylindrical wire bond portion 736 that is integral therewith. In aparticular embodiment such as shown in FIG. 13D, the cylindrical portionof a wire bond 732D that is integral with the ball-shaped portion 738Dcan project beyond a surface 752 of the encapsulant layer 751 of thepackage. Alternatively, as seen in FIG. 13E, the cylindrical portion ofa wire bond 732D may be fully covered by the encapsulant layer. In suchcase, as seen in FIG. 13E, the ball-shaped portion 738D of the wire bond732D may in some cases be partly covered by the encapsulation layer 751.

FIG. 13F further illustrates a wire bond 732F having a core 731 of aprimary metal and a metallic finish 733 thereon which includes a secondmetal overlying the primary metal, such as the palladium-clad copperwire or palladium-clad gold wire as described above. In another example,an oxidation protection layer of a non-metallic material such as acommercially available “organic solderability preservative” (OSP) can beformed on the unencapsulated portion of a wire bond to avoid oxidationthereof until the unencapsulated portion of the wire bond is joined to acorresponding contact of another component.

FIG. 14A illustrates a method by which a wire bond (FIG. 1) as describedherein can be shaped as a wire portion extending from a face of abonding tool 804, e.g., from a face 806 of a capillary-type bonding tool804, prior to bonding the shaped wire portion 800 to a bonding surface,e.g., to a conductive element 28 on a substrate, as will be furtherdescribed herein. As seen therein at stage A, a portion 800 of a wire,i.e., an integral portion having a predetermined length 802, of a metalwire such as a gold or copper wire or composite wire as described abovedescribed above relative to FIG. 1 extends out beyond a face 806 of abonding tool 804. In the examples which follow, the bonding tool 804 canbe a capillary having an opening in the face 806 thereof beyond whichthe wire portion extends. However, while the examples below refer to thebonding tool as a capillary, unless otherwise noted, the bonding toolcan be either be a capillary or a different type of bonding tool, suchas an ultrasonic or thermosonic bonding tool or wedge-bonding tool, forexample.

In order to arrange for a predetermined length of the metal wire toextend outward beyond the capillary face 806, the initial wire lengthcan be set by using the bonding tool 804 to bond the wire to a bondingsurface in a prior stage of processing, e.g., by a stitch-bonding methodor by a ribbon-bonding method. In an embodiment, when employing theribbon-bonding method, the ribbon can be one or more flat surfaces, andcan be polygonal in cross-section, such as a rectangular cross-section.Thereafter, the face 806 of the bonding tool can be moved relative tosuch bonding surface such that the bonding tool face 806 then isdisposed at a greater height above a plane in which such bonding surfacelies and the wire portion having the predetermined length extends beyondthe capillary face 806. Thus, the movement of the bonding tool relativeto the bonding surface can cause the wire portion 800 having thepredetermined length to be drawn out of the bonding tool. Thereafter,the wire can be severed at the boundary between the stitch-bond to thebonding surface and the wire portion 800. In this way, the wire portion800 is severed at the end 838 thereof. In one example, to sever the wireportion 800, the wire can be clamped at a location above the capillaryface and the clamped wire then can be tensioned so as to cause theclamped wire to break adjacent to the bonded part of the wire andthereby free the end 838 of the wire portion 800 from the bonded secondwire portion. The wire can be tensioned by exerting a force on at leastone of the capillary or the bonding surface relative to the other, e.g.,such as by pulling the capillary in an at least partially verticaldirection relative to a direction the wire extends through thecapillary. At that time, the wire portion 800 may extend in a straightdirection 801 away from a face 806 of the capillary. In one example, thedirection 801 may be perpendicular to the face 806 of the capillary.

In shaping the wire portion 800, the capillary and a forming surface,e.g., surface 812 within a channel or groove of a forming element 810,are positioned relative to one another such that an end 838 of the wireportion 800 that extends beyond the capillary face 806 is positioned ata greater depth 802 from the capillary face 806 than a depth 803 of theforming surface 812 below the capillary face. The forming element 810may be one or more tools or elements which together have surfacessuitable to assist in the forming, i.e., shaping, of the wire portionprior to the wire portion being bonded to the conductive element of thesubstrate.

As seen at stage B, at least one of the capillary 804 or a formingsurface 812 can be moved relative to one another such that the wireportion 800 moves relative to the forming surface 812 in at least afirst direction 814 parallel thereto so as to bend the wire portion 800towards the capillary 804. For example, as illustrated in FIG. 14A,movement of the capillary 804 relative to a first forming surface 812can cause the wire portion to be bent away from an initial direction 801as seen at stage A such that at least a part of the wire portion 800extends along the capillary face 806. In one example, the first formingsurface 812 can be a surface within a groove extending in the firstdirection 814 along a forming element 810, wherein the first directioncan be parallel to the capillary face 806. For example, groove 815 canbe open to a second surface 813 of the forming element which confrontsthe capillary face 806. As seen at stage B during the shaping orpre-forming process, the wire portion 800 may extend into groove and mayextend in the first direction parallel to the surface 812 and parallelto a direction 814 of movement of the capillary 804 as seen at stage Bof FIG. 14A.

Thereafter, after the wire-shaping performed in stage B, in stage C thecapillary 804 can be moved in a second direction 817 which is transverseto directions parallel to the capillary face 806. During this stage ofprocessing, an exposed wall 820 of the capillary which extends away fromthe capillary face 806 may confront a second forming surface 864. Insuch way, movement of the capillary 804 in direction 817 can cause thewire portion 800 to be bent in a direction towards the exposed wall 820.In one example, the second forming surface 864 can be a surface offorming element 810, the second forming surface 864 extending away fromthe first forming surface 812. In one example, the second formingsurface can extend at an angle 865 relative to the first forming surface812 which may be the same as an angle 867 at which the exposed wall ofthe capillary extends relative to the capillary face 806. As seen atstage C of FIG. 14A, the movement of the capillary can cause a part ofthe wire portion 800 to project upwardly in a direction 818 along theexposed wall 820 of the capillary. Capillary or bond tool 804 may have agroove, flat side or other wire-guiding feature on exposed wall thereofto help guide wire there. The second forming surface 864 can bevertical, i.e., at an angle normal to the face of the bonding tool, whenthe bonding tool has a vertical wall (as shown in FIG. 35). The wireportions 800 may be formed from copper or copper alloy, and may haverelatively small diameter, e.g., 25 micrometers, such that a largenumber of input/output connections, e.g., 1000-2000 per package.

Stage C illustrates further processing of the wire portion 800 byrelative movement of the capillary 804 and a another forming surface 823in a direction transverse to the capillary face 806, for example, indirection 817, or in a direction perpendicular to the face 806 of thecapillary, the forming surface 823, or perpendicular to both surfaces.In terms of a purpose thereof, the forming surface 823 can be considereda “coining surface.” When carried through to completion, such relativemovement coins a part 825 of the wire portion disposed between thecapillary face 806 and the coining surface 823.

FIG. 14B is a fragmentary plan view of a shaped wire portion 800 from aposition below the capillary face 806 and FIG. 14C is a sectional viewfurther illustrating the position of the wire portion 800 between thecapillary face 806 and the coining surface 823 and parts of the wireportion as will be further described below. For example, FIG. 14Billustrates the shaped wire portion from a position below the coiningsurface 823 and looking towards the coined part 825 of the wire portion800 such that the capillary face 806 appears at a position above, i.e.,behind the coined part 825 of the wire portion in FIG. 14B. A part 827of the wire portion 800 aligned with the opening 808 in the capillaryface is also illustrated in FIGS. 14B, 14C. A part 831 of the wireportion 800 which extends away from the capillary face 806 along theexposed wall 820 (FIG. 14A) of the capillary is also shown in FIGS.14A-B. The parts 827 and 831 of the wire portion typically retaincylindrical cross-section after the processing described above inaccordance with FIG. 14A, these parts 827, 831 of the wire possiblyavoiding some of the flattening of the wire when the part 825 of thewire portion 800 is coined between the capillary face 806 and thecoining surface 823.

When the coining surface 823 is flat, in one example, at least a part ofa face 833 of the coined part 825 of the wire portion facing the coiningsurface 823 can also be flat. This flat face 833 then will be furtheravailable to be bonded by the capillary to a bonding surface of aconductive element 28 such as described above.

However, alternatively, the coining surface 823 may in some cases bepatterned such that it has raised and recessed features therein. In suchcase, the face 833 of the coined part 825 of the wire portion maylikewise be patterned face of raised and recessed features which facesaway from the capillary face 806. Such patterned face of the coined part825 would then be available to be bonded to a bonding surface of aconductive element 28.

After pre-shaping the wire portion 800 in this manner, the capillary canbe used to bond the pre-shaped wire portion 800 to a bonding surface ofa conductive element 28 of a substrate (FIG. 1). To form the wire bond,the wire is now moved away from the forming unit 810 and moved towardsthe conductive element 28 (FIG. 1) of the substrate where the capillarythen stitch bonds the coined wire portion 825 to the conductive element28, with the end 838 of the wire portion being the remote end 38(FIG. 1) of the wire bond remote from the conductive element 28.

The provision of a wire portion 800 having a coined part 825 with alower surface 833 which can be flat, or alternatively, patterned, or aface that is partly flat and partly patterned, can assist in forming agood bond between the shaped wire portion 800 and the bonding surface ofthe conductive element 28. As can be understood from FIG. 14A, whenready for bonding to the bonding surface, the shaped wire portion 800 israther long relative to the diameter of the wire, and a long extensionof the wire, being much if not most of the shaped wire portion isunsupported except by the bonding surface of the conductive element 28(FIG. 1) when the wire portion is being bonded thereto.

With the coining of the wire portion, the stability of the wire portioncan be improved when the wire portion is being bonded to the bondingsurface. For example, the flattening or patterning of the coined part825 of the wire may help increase friction between the lower surface 833of the coined part 825 and the bonding surface when the capillaryapplies force to the wire portion to bond it to the bonding surface, andmay decrease a tendency of the wire to pivot, roll or otherwise movewhen the bonding force is applied. In this, way, the coined part 825 ofthe wire portion can overcome a possibility that the wire having theoriginal cylindrical shape would pivot or roll when force is applied bythe face 806 of a capillary to bond the wire to the bonding surface.FIG. 15 further illustrates an example of movement of the capillary oversurfaces of a forming element 810 in a method according to an embodimentof the invention. As seen therein, in a particular example, the formingelement 810 may have a first opening or depression 830 in which thecapillary 804 is disposed at an initial stage (FIG. 14A, stage A) ofwire-shaping, when the wire portion 800 extends outwardly beyond anopening 808 of the capillary. The opening 830 or depression may includea tapered portion, channel or groove 832 which can help guide the wireportion 800 onto a surface 812 at stage B, and which may also guide thewire portion a particular portion of the surface 812. Such taperedportion can be tapered in such way that the tapered portion growssmaller in a direction towards the surface 812 to help engage and guidethe wire portion to a particular location.

The forming unit may further include a channel 834 or groove for guidingthe segment 800 in stage B of the process. As further shown in FIG. 15,the forming unit may include a further opening or depression or 840 inwhich an interior surface 816 thereof may function as the second formingsurface along which the capillary moves in stage C of the process tocause the metal wire segment to be bent in direction 818 against theexterior wall 820 of the capillary. In one example, the second formingsurface within the opening 816 or depression can include a channel orgroove 819 which is recessed relative to another interior surface withinthe opening 816. In a particular example, the coining surface 823 can bedisposed within the opening 816. Optionally, a groove may be formed onthe tool or on the capillary itself, in addition to or as an alternativeto groove 819. For example, as shown in FIG. 14C, a groove 811 may beformed on the capillary face 806 in addition to or as an alternative togroove 819.

In an embodiment, a variation of the capillary shown in FIG. 14 can beused that incorporates a vertical or near-vertical side wall 2820. Asshown in FIG. 35, the side wall 2820 of capillary 2804 can besubstantially vertical or, in other words, parallel to the wire segment2800 or perpendicular to the face 2806 of the capillary 2804. This canallow for formation of a wire bond (32 in FIG. 1) that is closer tovertical, i.e., closer to an angle of 90° away from the surface of thefirst surface of the substrate, than achieved by a side wall at anexterior of the capillary that defines an angle having a measuresubstantially less than 90°, such as the capillary shown in FIG. 14. Forexample, using a forming tool 2810, a wire bond can be achieved that isdisposed at an angle from the first portion which extends between 25°and 90°, or between about 45° and 90° or between about 80° and 90° withrespect to the first wire portion 2822.

In another variation, a capillary 3804 can include a surface 3808 thatprojects beyond the face 3806 thereof. This surface 3808 can beincluded, for example over the edge of the side wall 3820, and may forma lip. In the method for forming a wire bond (32 in FIG. 1, forexample), the capillary 3804 can be pressed against the first portion3822 of the wire segment 3800 during forming of wire segment, e.g., whenthe capillary moves in a direction along a forming surface 3816 whichextends in a direction away from surface 3812. In this example, surface3808 presses into the first portion 3822 at a location near the bendfrom which the remaining wire segment 3800 extends. This can causedeformation of the wire segment 3800 such that it may press against thewall 3820 of the capillary 3804 and move to a somewhat more verticalposition once the capillary 3804 is removed. In other instances, thedeformation from the surface 3808 can be such that a position of thewire segment 3800 can be substantially retained when the capillary 3804is removed.

FIGS. 16A-16C illustrate stages of shaping a wire and a set of formingsurfaces used therein in a method of forming wire bonds according to anembodiment of the invention. FIG. 16A shows a forming element 850 whichcan be used in shaping a portion of a wire extending beyond a face of abonding tool prior to forming a bond between the wire portion and abonding surface of a substrate. As in the above-described example (FIGS.14A-C), the bonding tool can be a capillary type tool or other bondingtool such as an ultrasonic bonding tool or wedge-bonding tool. As seenin FIG. 16A, a recess 852 may extend in an inward direction from an edge851 of the forming element 850. The recess 852 can be configured toreceive a portion of a wire extending from a face of a bonding tool,such as a wire portion extending from a face of the capillary or othertype bonding tool. In a particular embodiment, the recess mayadditionally include a tapered portion or channel 854 having width 855somewhat larger than the diameter of a wire to be shaped therein. As atapered portion, the width can become smaller in a direction towards thefirst forming surface 860 such that the tapered portion can help guidethe wire towards a particular area 862, e.g., a central area, of thefirst forming surface. The first forming surface may be a flat, i.e.,planar or substantially planar surface which extends in first and secondtransverse directions, and area 862 of the first forming surface canlikewise be flat. In such way, the first forming surface can extend indirections parallel to a face of the bonding tool or capillary whenshaping the wire portion in stage of the method such as seen in stage Bas seen in FIG. 14.

The forming element 850 typically also includes a second forming surface864 which extends away from the first forming surface 860. In theexample seen in FIG. 16A, the second forming surface 864 extends awayfrom the first forming surface 860. The second forming surface 864 maybe disposed in a second recess 866 extending inwardly from an edge 861of the forming element opposite edge 851. In one example, an angle 865at which the second forming surface 864 slopes away from the firstforming surface 860 can be the same as an angle 867 at which an exposedwall 868 of the bonding tool slopes away from the face of the bondingtool, as seen in FIG. 14A.

The forming element 860 typically has an additional surface, which canbe a “coining” surface 870 against which a face of the bonding tool orcapillary can be pressed during the wire-shaping process to coin a partof the wire that is disposed between the face 806 of the bonding tooland the coining surface 870.

FIG. 16B illustrates a stage of shaping the wire portion 800 (FIG. 14A)when the capillary or other type bonding tool 804 has moved into aposition in which the shaping of the wire portion extending beyond thebonding tool face is about to begin. At such time, the wire portion 800extends into the recess 852 of the forming element 850. FIG. 16Billustrates a stage of shaping the wire analogous to stage A shown inFIG. 14A, which further shows the direction 814 of movement of thebonding tool along the forming element 850.

FIG. 16C illustrates a further stage of shaping the wire portion 800(FIG. 14A) when the bonding tool 804 has moved in direction 814 along afirst forming surface 860 or 862, these surfaces having been describedabove relative to FIG. 16A. A part 831 of the wire portion is shownextending away from an opening 808 of the bonding tool similar to thewire portion seen at stage B in FIG. 14A.

FIG. 16D further illustrates a stage of shaping the wire analogous tothat seen at stage C of FIG. 14A in which the bonding tool 804 has movedto a position aligned with a second recess in the forming element. Atthis time, the part 831 of the wire portion which extends away from theopening can be bent towards the exposed wall of the bonding tool, asshown and described above with respect to FIG. 14A. In addition, at thistime, as shown and described above regarding stage C of FIG. 14A, thebonding tool 804 can coin the wire portion by pressing a part of thewire portion between the face of the bonding tool and the coiningsurface, the coining surface 870 being as shown in FIG. 16A. FIG. 16E isa diagrammatic view showing that wire bonds 932 formed according to oneor more of the methods described herein can have ends 938 which areoffset from their respective bases 934. In one example, an end 938 of awire bond can be displaced from its respective base such that the end938 is displaced in a direction parallel to the surface of the substratebeyond a periphery of the conductive element to which it is connected.In another example, an end 938 of a wire bond can be displaced from itsrespective base 934 such that the end 938 is displaced in a directionparallel to the surface of the substrate beyond a periphery 933 of theconductive element to which it is connected.

FIGS. 17A-C illustrate an example of using a bonding tool to shape thewire portion at a forming station 880. The forming station can beassembled with, e.g., mounted to a structure to which a wirebondingstation is also assembled, so that a wire portion, after being shaped atthe forming station by the bonding tool, can then be moved by thebonding tool to the wirebonding station and then bonded to a bondingsurface on a substrate, microelectronic element or other component. Asseen in FIG. 17A, a bond tool 804 portion of a bond head 844 can firstbe moved to the forming station 880 where the wire portion can be shapedby movement of the bond tool as described above. For example, the bondhead 844 or a portion of the bond head can pivot about an axis to movethe bonding tool to the forming station 880.

The forming element 850 can be oriented in a specific way relative tothe wirebonding station to reduce the extent of movement required by thebond head or bond tool between the forming station and wirebondingstation. As seen in FIG. 17A, in one example, the forming element 850 atthe forming station can be oriented such that the recess 852 describedabove relative to FIG. 16A may be at a remote position relative to thewirebonding station and the coining surface 870 may be at a positioncloser to, i.e., adjacent to the wirebonding station. In anotherexample, the recess 852 and the coining surface 870 can be oriented inthe opposite way with the recess 852 closer to the wirebonding stationthan the coining surface. In yet another example, it may be possible forthe forming element to be in one orientation during the shaping of thewire portion, and then the orientation of the forming element can bereversed to permit greater freedom of movement of the bond tool with theshaped wire portion thereon prior to moving the shaped wire portion intofinal position for bonding.

FIG. 17B illustrates a position of the bond tool 804 and bond head 844at the completion of shaping the wire portion, which may include coiningthe wire portion as described above. At such time, the bond tool canthen be moved from the position at the forming station 880 (FIG. 17B)into position (FIG. 17C) at the wirebonding station 882 where the shapedwire portion then is bonded to a bonding surface on a component 884.

FIGS. 18A-18C illustrate another variation in which the bond tool 1804and a forming element 1810, such as the forming element 810 or 850 asdescribed above, can be assembled with a common bond head 1844. In oneexample, the forming element 1810 can be affixed to or otherwise carriedon the bond head 1844 such that movement of the bond head transports theforming element 1810 attached thereto as well as the bonding tool.However, the forming element 1810 can move relative to the bonding toolso as to assist in the shaping of the wire portion prior to bonding ofthe wire portion, but then the forming element 1810 can be moved awayfrom such forming position once the wire has been shaped and is ready tobe bonded to a component 1884 as seen in FIG. 18C.

In one example, the forming element 1810 can be carried on a pivotableor otherwise movable arm 1812, for relative movement between the bondingtool 1804 and the arm 1812. Alternatively, the forming element 1810 maybe provided on an arm having a fixed position during operation, and thebonding tool instead can move relative to the forming element. In anexample of operation, at a stage of processing shown in FIG. 18A, thebonding tool 1804 and the forming element 1810 can be arranged in aposition as shown in FIG. 18A in which the forming element 1810 and thebonding tool are at spaced apart positions. When so arranged as in FIG.18A, a shaped wire portion can be bonded to a bonding surface of aconductive element or other feature on component 1884.

Thereafter, as seen in FIG. 18B, relative motion between the formingelement and the bonding tool places the bonding tool and the formingelement at positions in which the wire portion can be shaped such asdescribed above relative to one or more of FIGS. 14-16. Thus, in aparticular example, during the shaping of the wire portion, the bondingtool can remain at a position above or in close proximity to a component1884 to be wire bonded, which may be above or in close proximity to aparticular bond site on the component 1884. In that way, the movement ofthe bond head can be reduced, and thereby it may be possible to reducean amount of time needed to shape the wire portion prior to bonding thewire portion to the bonding surface on the component. As further seen inFIG. 18C, after the wire portion has been shaped, the forming element1810 may move to a third position as seen in FIG. 18C, and while theforming element is in such position, the bonding tool may then bond theshaped wire portion to the component.

FIG. 19 illustrates a variation of the above-described pre-formingprocess which can be used to form wire bonds 332Cii (FIG. 5) having abend and which have ends 1038 displaced in a lateral direction 1014Afrom the portions 1022 which will be stitch-bonded to the conductiveelements as bases 1034 of the wire bonds.

As seen in FIG. 19, the first three stages A, B, and C of the processcan be the same as described above with reference to FIG. 14A. Then,referring to stages C and D therein, a portion 1022A of the wire bondadjacent the face 806 of the capillary 804 is clamped by a tool whichcan be integrated with the forming unit. The clamping may be performedactively or passively as a result of the motion of the capillary overthe forming unit. In one example, the clamping can be performed bypressing a plate having a non-slip surface thereon onto the metal wiresegment 800 to preclude movement of the metal wire segment.

While the metal wire segment 800 is clamped in this manner, at stage Dshown in FIG. 19, the capillary or bond tool 804 moves in a direction1016 along a third surface 1018 of the forming unit 1010 and feeds out alength of wire equivalent to the distance moved along surface 1018.Thereafter, at stage E, the capillary is moved downwardly along a thirdsurface 1024 of the forming unit to cause a portion of the wire to bebent upwardly along an exterior surface 1020 of the capillary 804. Insuch way, an upwardly projecting portion 1026 of the wire can beconnected to another upwardly projecting portion 1036 by a third portion1048 of the metal wire.

After formation of the wire segment and bonding thereof to a conductiveelement to form a wire bond, particularly of the ball bond typediscussed above, the wire bond (32 in FIG. 1, for example) is thenseparated from a remaining portion of the wire within the capillary(such as 804 in FIG. 14A). This can be done at any location remote fromthe base 34 of the wire bond 32 and is preferably done at a locationremote from the base 34 by a distance at least sufficient to define thedesired height of the wire bond 32. Such separation can be carried outby a mechanism disposed within the capillary 804 or disposed outside ofthe capillary 804, between the face 806 and the base 34 of the wire bond32. In one method, the wire segment 800 can be separated by effectivelyburning through the wire 800 at the desired separation point, which canbe done by application of a spark or flame thereto. To achieve greateraccuracy in wire bond height, different forms of cutting the wiresegment 800 can be implemented. As described herein, cutting can be usedto describe a partial cut that can weaken the wire at a desired locationor cutting completely through the wire for total separation of the wirebond 32 from the remaining wire segment 800.

In one example shown in FIG. 32 a cutting blade 805 can be integratedinto the bond head assembly, such as within capillary 804. As shown, anopening 807 can be included in the side wall 820 of the capillary 804through which cutting blade 805 can extend. The cutting blade 805 can bemoveable in and out of the interior of the capillary 804 so that it canalternately allow the wire 800 to freely pass therethrough or engage thewire 800. Accordingly, the wire 800 can be drawn out and the wire bond32 formed and bonded to a conductive element 28 with the cutting blade805 in a position outside of the capillary interior. After bondformation, the wire segment 800 can be clamped using a clamp 803integrated in the bond head assembly to secure the position of the wire.The cutting blade 803 can then be moved into the wire segment to eitherfully cut the wire or to partially cut or weaken the wire. A full cutcan form end surface 38 of the wire bond 32 at which point the capillary804 can be moved away from the wire bond 32 to, for example, formanother wire bond. Similarly, if the wire segment 800 is weakened by thecutting blade 805, movement of the bond head unit with the wire stillheld by the wire clamp 803 can cause separation by breaking the wire 800at the area weakened by the partial cut.

The movement of the cutting blade 805 can be actuated by pneumatics orby a servo motor using an offset cam. In other examples the cuttingblade 805 movement can be actuated by a spring or a diaphragm. Thetriggering signal for the cutting blade 805 actuation can be based on atime delay that counts down from formation of the ball bond or can beactuated by movement of the capillary 804 to a predetermined heightabove the wire bond base 34. Such a signal can be linked to othersoftware that operates the bonding machine so that the cutting blade 805position can be reset prior to any subsequent bond formation. Thecutting mechanism can also include a second blade (not shown) at alocation juxtaposed with blade 805 with the wire therebetween, so as tocut the wire by movement of one or more of the first and second bladesrelative to the other of the first and second blades, such as in oneexample, from opposite sides of the wire.

In another example, a laser 809 can be assembled with the bond head unitand positioned to cut the wire. As shown in FIG. 33, a laser head 809can be positioned outside of capillary 804 such as by mounting theretoor to another point on the bond head unit that includes capillary 804.The laser can be actuated at a desired time, such as those discussedabove with respect to the cutting blade 805 in FIG. 32, to cut the wire800, forming end surface 38 of the wire bond 32 at a desired heightabove the base 34. In other implementations, the laser 809 can bepositioned to direct the cutting beam through or into the capillary 804itself and can be internal to the bond head unit. In an example, acarbon dioxide laser can be used or, as an alternative, a Nd:YAG or a Cuvapor laser could be used.

In another embodiment a stencil unit 824 as shown in FIGS. 34A-C can beused to separate the wire bonds 32 from the remaining wire segment 800.As shown in FIG. 34A, the stencil 824 can be a structure having a bodythat defines an upper surface 826 at or near the desired height of thewire bonds 32. The stencil 824 can be configured to contact theconductive elements 28 or any portions of the substrate 12 or packagestructure connected thereto between the conductive elements 28. Thestencil includes a plurality of holes 828 that can correspond to thedesired locations for the wire bonds 32, such as over conductiveelements 28. The holes 828 can be sized to accept the capillary 804 ofthe bond head unit therein so that the capillary can extend into thehole to a position relative to the conductive element 28 to bond thewire 800 to the conductive element, 28 to form the base 34, such as byball bonding or the like. In one example, the stencil can have holesthrough which individual ones of the conductive elements are exposed. Inanother example, a plurality of the conductive elements can be exposedby a single hole of the stencil. For example, a hole can be achannel-shaped opening or recess in the stencil through which a row orcolumn of the conductive elements are exposed at a top surface 826 ofthe stencil.

The capillary 804 can then be moved vertically out of the hole 828 whiledrawing out the wire segment to a desired length. Once cleared from thehole 828, the wire segment can be clamped within the bond head unit,such as by clamp 803, and the capillary 804 can be moved in a lateraldirection (such as parallel to the surface 826 of stencil 824) to movethe wire segment 800 into contact with an edge 829 of the stencil 824defined by the intersection of the surface of the hole 828 and theoutside surface 826 of the stencil 824. Such movement can causeseparation of the wire bond 32 from a remaining portion of the wiresegment 800 that is still held within the capillary 804. This processcan be repeated to form the desired number of wire bonds 32 in thedesired locations. In an implementation, the capillary can be movedvertically prior to wire separation such that the remaining wire segmentprojects beyond the face 806 of the capillary 804 by a distance 802sufficient to form a subsequent ball bond. FIG. 34B shows a variation ofstencil 824 in which the holes 828 can be tapered such that they have adiameter that increases from a first diameter at surface 826 to agreater diameter away from surface 826. In another variation, as shownin FIG. 34C, the stencil can be formed having an outer frame 821 havinga thickness sufficient to space apart surface 826 at the desireddistance from substrate 12. Frame 821 can at least partially surround acavity 823 configured to be positioned adjacent substrate 12 with athickness of the stencil 824 extending between the surface 826 and theopen area 823 such that the portion of stencil 824 that includes theholes 828 is spaced apart from the substrate 12 when positioned thereon.

FIGS. 20A-C illustrate one technique that can be used when forming theencapsulation layer by molding in order that unencapsulated portions 39(FIG. 1) of the wire bonds project beyond a surface 44 of theencapsulation layer 42. Thus, as seen in FIG. 20A, a film-assistedmolding technique can be used by which a temporary film 1102 is placedbetween a plate 1110 of a mold and a cavity 1112 in which a subassemblyincluding the substrate, wire bonds 1132 joined thereto, and a componentsuch as a microelectronic element may be joined. The film 1102 may beformed from ethylene tetrafluoroethylene. The film 1102 may cover atleast 10% of the length of the wire bonds and may be at least 50micrometers. In one embodiment, the film 1102 may be 200 micrometers,although the film can be thicker or thinner than 200 micrometers. FIG.20A further shows a second plate 1111 of the mold which can be disposedopposite the first plate 1110.

Then, as seen in FIGS. 20B-20C, when the mold plates 1110, 1111 arebrought together, the ends 1138 of wire bonds 1132 can project into thetemporary film 1102. When a mold compound is flowed in the cavity 1112to form encapsulation layer 1142, the mold compound does not contact theends 1138 of the wire bonds because they are covered by the temporaryfilm 1102. After this step, the mold plates 1110, 1111 are removed fromthe encapsulation layer 1142, the temporary film 1102 can now be removedfrom the mold surface 1144, which then leaves the ends 1138 of the wirebonds 1132 projecting beyond the surface 1144 of the encapsulationlayer.

The film-assisted molding technique may be well adapted for massproduction. For example, in one example of the process, a portion of acontinuous sheet of the temporary film can be applied to the mold plate.Then the encapsulation layer can be formed in a cavity 1112 that is atleast partially defined by the mold plate. Then, a current portion ofthe temporary film 1102 on the mold plate 1110 can be replaced byautomated means with another portion of the continuous sheet of thetemporary film. In a variation of the film-assisted molding technique,instead of using a removable film as described above, a water-solublefilm can be placed on an inner surface of the mold plate 1110 prior toforming the encapsulation layer. When the mold plates are removed, thewater soluble film can be removed by washing it away so as to leave theends of the wire bonds projecting beyond the surface 1144 of theencapsulation layer as described above.

In an example of the method of FIGS. 20A-B, the heights of the wirebonds 1132 above the surface 1144 of encapsulation layer 1142 can varyamong the wire bonds 1132, as shown in FIG. 37A. A method for furtherprocessing the package 1110 such that the wire bonds 1132 project abovesurface 1142 by substantially uniform heights is shown in FIGS. 37B-Dand utilizes a sacrificial material layer 1178 that can be formed tocover the unencapsulated portions of the wire bonds 1132 by applicationthereof over surface 1144. The sacrificial layer 1178 can then beplanarized to reduce the height thereof to the desired height for wirebonds 1132, which can be done by lapping, grinding, or polishing or thelike. As also illustrated in the Figures, the planarization of thesacrificial layer 1178 can begin by reducing the height thereof to apoint where the wire bonds 1132 become exposed at the surface of thesacrificial layer 1178. The planarization process can then alsoplanarize the wire bonds 1132 simultaneously with the sacrificial layer1178 such that, as the height of the sacrificial layer 1178 is continuedto be reduced, the heights of the wire bonds 1132 are also reduced. Theplanarization can be stopped once the desired height for the wire bonds1132 is reached. It is noted that in such a process the wire bonds 1132can be initially formed such that their heights, while beingnon-uniform, are all greater than the targeted uniform height. Afterplanarization reduces the wire bonds 1132 to the desired height, thesacrificial layer 1178 can be removed such as by etching or the like.The sacrificial layer 1178 can be formed from a material that can allowfor removal by etching using an etchant that will not significantlyaffect the encapsulant material. In one example, the sacrificial layer1178 can be made from a water soluble plastic material.

FIGS. 21A and 21B illustrate another method by which unencapsulatedportions of the wire bonds can be formed which project beyond a surfaceof the encapsulation layer. Thus, in the example seen in FIG. 21A,initially wire bonds 1232 may be flush with or may not even be exposedat a surface 1244 of the encapsulation layer 1242. Then, as shown inFIG. 21B, a portion of the encapsulation layer, e.g., a moldedencapsulation layer, can be removed to cause the ends 1238 to projectbeyond the modified encapsulation layer surface 1246. Thus, in oneexample, laser ablation can be used to recess the encapsulation layeruniformly to form a planar recessed surface 1246. Alternatively, laserablation can be performed selectively in areas of the encapsulationlayer adjoining individual wire bonds.

Among other techniques that can be used to remove at least portions ofthe encapsulation layer selectively to the wire bonds include “wetblasting” techniques. In wet blasting, a stream of abrasive particlescarried by a liquid medium is directed towards a target to removematerial from the surface of the target. The stream of particles maysometimes be combined with a chemical etchant which may facilitate oraccelerate the removal of material selectively to other structure suchas the wire bonds which are to remain after wet blasting.

In the example shown in FIGS. 38A and 38B, in a variation of the methodshown in FIGS. 21A and 21B, wire bond loops 1232′ can be formed thathave bases 1234 a on conductive elements 1228 at one end and areattached to a surface of the microelectronic element 1222 at the otherend 1234 b. For attachment of the wire bond loops 1232′ to themicroelectronic element 1222, the surface of the microelectronic element1223 can be metalized such as by sputtering, chemical vapor deposition,plating or the like. The bases 1234 a can be ball bonded, as shown, oredge bonded, as can the ends 1232 b joined to the microelectronicelement 1222. As further shown in FIG. 38A, the dielectric encapsulationlayer 1242 can be formed over substrate 1212 to cover the wire bondloops 1232′. The encapsulation layer 1242 can then be planarized, suchas by grinding, lapping, polishing, or the like, to reduce the heightthereof and to separate the wire bond loops 1232′ into connection wirebonds 1232A that are available for joining to at least the end surfaces1238 thereof for electrical connection to the conductive elements 1228and thermal dissipation bonds 1232B that are joined to themicroelectronic element 1222. The thermal dissipation bonds can be suchthat they are not electrically connected to any of the circuitry of themicroelectronic element 1222 but are positioned to thermally conductheat away from the microelectronic element 1222 to the surface 1244 ofthe encapsulation layer 1242. Additional processing methods can beapplied to the resulting package 1210′, as described elsewhere herein.

FIGS. 22A-22E illustrate yet another method of forming an encapsulationlayer by molding in which unencapsulated portions of wire bonds protrudethrough the encapsulation layer. As shown in FIG. 22A, wire bonds 1302are molded onto a substrate 1304. The wire bonds 1302 may include a wire1306 and a base 1308, which may be connected to a conductive element,such as an electroless nickel electroless palladium immersion gold(ENEPIG) material. The wire 1306 may be formed from a material includingcopper or a copper alloy. A raised material region 1310, such as a dam,may be formed at or on a face 1312 of the substrate 1304, for example,along the perimeter of the face 1312 of the semiconductor region withthe wire bonds 1302 positioned within an area circumscribed or at leastpartially bordered by the region 1310. In a particular example, theregion 1310 may be formed from a photoimageable material, such as asolder mask.

As shown in FIG. 22B, a stiffening layer 1314, which in one case may bereferred to as wire locking material 1314, can be deposited onto theface 1312 of substrate 1304 and be contained fully or at least partly bythe region 1310. In this way, the region 1310 may at least partly definethe area in which the wire locking material is to be provided on surface1312. The wire lengths can be as described above, and in a particularexample, each wire 1304 may have a length within an approximate range of150 to 200 micrometers. In one example, the wire locking material 1314may be dispersed and distributed using a spin-on process. The wirelocking material 1314 when deposited may cover a portion of the wire1306 extending a distance from the face 1312 of the substrate 1304,e.g., the locking material may cover approximately 50 micrometers orapproximately a quarter to a third of the length of the wire. The wirelocking material 1314 increases the stiffness or the rigidity of thewire 1306, inhibiting flexing or bending the wire. In one example, thewire locking material may be a silica filled liquid encapsulant, whichtypically is stiffer than an equivalent non-filled encapsulant, such asthat sold under the trade name NoSWEEP™.

As shown in FIG. 22C, when forming an encapsulation, the wires 1306 maybe inserted into a removable film 1316, which may be the same as orsimilar to the temporary film 1102 described above with respect to FIGS.20A-20C, and may be formed from ethylene tetrafluoroethylene. In anembodiment, the film 1316 may cover at least 10% of the length of thewire bonds and may be at least 50 micrometers. In one embodiment, thefilm 1316 may have a thickness that is 200 micrometers, although thefilm thickness can be greater than or less than 200 micrometers. Thefilm 1316 prevents the end portions 1306 e of the wires 1306 from beingcovered by a second material, e.g., a mold compound or other encapsulant1318, such as during formation of the encapsulation layer 42 asdescribed above.

As described above with respect to FIGS. 20A and 20B, and as shown inFIG. 22D, the encapsulant 1318 may be deposited or flowed within aninternal cavity of a mold in which the substrate and attached wire bondshave been placed, and a film 1316 has been provided similar to film 1102shown in FIGS. 20A-20C. The reinforcement and stiffening of the wires1306 by depositing the wire locking material 1314 around a portion ofthe wires, facilitates penetration of the wires 1306 into the film 1316with less movement of the wires than would otherwise be achievable.After depositing the encapsulant 1318 to cover portions of the wires1306, the film 1316 may be removed exposing the ends 1306 e of the wiresto form microelectronic assembly 1302 as seen in FIG. 22E.

Another method for forming wire bonds 2632 to a predetermined height isshown in FIGS. 39A-C. In such a method a sacrificial encapsulation layer2678 can be formed over the surface 2614 of substrate 2612, at least inthe second 2620 region thereof. The sacrificial layer 2678 can also beformed over the first region 2618 of the substrate 2612 to cover themicroelectronic element 2622 in a similar manner to the encapsulationlayers described with respect to FIG. 1, above. The sacrificial layer2678 includes at least one opening 2679 and in some embodiments aplurality of openings 2679 to expose the conductive elements 2628. Theopenings 2679 can be formed during molding of the sacrificial layer 2678or after molding by etching, drilling, or the like. In one embodiment, alarge opening 2679 can be formed to expose all of the conductiveelements 2628, while in other embodiments a plurality of large openings2679 can be formed to expose respective groups of conductive elements2628. In further embodiments, openings 2629 can be formed thatcorrespond to individual conductive elements 2628. The sacrificial layer2678 is formed having a surface 2677 at a desired height for the wirebonds 2632 such that the wire bonds 2632 can be formed by bonding bases2634 thereof to the conductive elements 2628 and then drawing out thewire to reach the surface 2677 of the sacrificial layer 2678. Then, thewire bonds can be drawn laterally of the opening to overlie portions ofthe surface 2677 of the sacrificial layer 2678. The capillary of thebond forming instrument (such as capillary 804 as shown in FIG. 14) canbe moved to press the wire segment into contact with the surface 2677such that the pressure on the wire between the surface 2677 and thecapillary causes the wire to sever on surface 2677, as shown in FIG.39A.

The sacrificial layer 2678 can then be removed by etching or anothersimilar process. In an example, the sacrificial layer 2678 can be formedfrom a water soluble plastic material such that it can be removed byexposure to water without affecting the other components of thein-process unit 2610″. In another embodiment, sacrificial layer 2678 canbe made from a photoimageable material such as a photoresist such thatit can be removed by exposure to a light source. A portion ofsacrificial layer 2678′ can remain between microelectronic element 2622and surface 2614 of substrate 2612 that can act as an underfillsurrounding solder balls 2652. After removal of the sacrificial layer2678 an encapsulation layer 2642 is formed over the in-process unit toform package 2610. The encapsulation layer 2642 can be similar to thosedescribed above and can substantially cover surface 2614 of substrate2612 and microelectronic element 2622. Encapsulation layer 2642 canfurther support and separate the wire bonds 2632. In the package 2610shown in FIG. 29C, the wire bonds include portions of the edge surfaces2637 thereof that are exposed at surface 2644 of the encapsulant 2642and extend substantially parallel thereto. In other embodiments, thewire bonds 2632 and the encapsulation layer 2642 can be planarized toform a surface 2644 with wire bonds that have end surfaces exposedthereon and substantially flush therewith.

The above-described embodiments and variations of the invention can becombined in ways other than as specifically described above. It isintended to cover all such variations which lie within the scope andspirit of the invention.

1. A method of forming a plurality of wire bonds connected to asubstrate, comprising: (a) positioning at least one of: a bonding tooland a portion of a wire extending downward beyond a face thereof; or aforming surface relative to one another such that an end of the wireportion extending downward beyond a face of the bonding tool ispositioned at a greater depth from the bonding tool face than theforming surface; (b) then moving the bonding tool along the firstforming surface in a first direction parallel to the face of the bondingtool so as to bend the wire portion towards the bonding tool; (c) thenmoving the bonding tool in a second direction transverse to the bondingtool face such that an exposed wall of the bonding tool extending awayfrom the bonding tool face confronts a second forming surface extendingaway from the first forming surface, whereby the wire portion is benttowards the exposed wall of the bonding tool; (d) coining a part of thewire portion between the bonding tool face and a coining surface; (e)using the bonding tool to bond the coined part of the wire portion to anelectrically conductive bonding surface of the substrate to form a wirebond, while leaving unbonded the end of the wire portion remote from thecoined part; and (f) repeating steps (a) through (e) to form a pluralityof the wire bonds to at least one of the bonding surface.
 2. The methodas claimed in claim 1, wherein the coining surface includes a groovehaving a depth less than a diameter of the wire portion and the coiningof the wire portion is performed to coin the part of the wire portionwith the groove of the coining surface.
 3. The method as claimed inclaim 1, wherein the bonding tool has a capillary out of which the wireportion extends and the face of the bonding tool is the face of thecapillary.
 4. The method as claimed in claim 1, wherein the bonding toolis a wedge-bonding tool.
 5. The method as claimed in claim 1, whereinthe bonding tool and the forming surfaces are assembled with a commonbond head.
 6. The method as claimed in claim 5, wherein the first andsecond forming surfaces are disposed at a forming station and at leaststeps (b), (c) are performed at the forming station, and at least step(e) is performed at a bonding station, wherein the bonding tool issupported by a bond head, and the method further comprises, prior tostep (d), moving the bond head and the bonding tool supported therebyfrom the forming station to the bonding station.
 7. The method asclaimed in claim 5, wherein the coining surface is disposed at theforming station and step (d) is performed at the forming station.
 8. Themethod as claimed in claim 1, wherein the wire portion is a first wireportion and the extending of the first wire portion in step (a) isperformed by bonding a second portion of the wire to a second bondingsurface, and then moving the bonding tool face to a greater height abovea plane in which the second bonding surface lies such that the firstwire portion is extended outward beyond the face of the bonding tool,then severing the wire to separate the first wire portion from thesecond wire portion.
 9. The method as claimed in claim 8, wherein thestep of severing the wire includes clamping the wire and tensioning theclamped wire to cause the clamped wire to break between the first andsecond wire portions.
 10. The method as claimed in claim 8, wherein thesevering the wire includes clamping the wire and tensioning the clampedwire to cause the clamped wire to break at a predetermined length. 11.The method as claimed in claim 8, wherein the severing includes clampingand tensioning a plurality of wires to cause the clamped wires to breakat a plurality of different predetermined lengths.
 12. The method asclaimed in claim 1, wherein the second forming surface slopes away fromthe first forming surface at a first angle to the first forming surface,and the exposed bonding tool wall slopes away from the bonding tool faceat the first angle.
 13. The method as claimed in claim 1, wherein thesecond forming surface is a channel recessed relative to at least onethird surface.
 14. The method as claimed in claim 1, wherein step (d)forms the coined part having resistance to movement in the lateraldirection when step (e) is performed to bond the wire portion to thebonding surface.
 15. The method as claimed in claim 1, wherein step (d)forms the coined part having resistance to rolling in the lateraldirection when step (e) is performed to bond the wire portion to thebonding surface.
 16. The method as claimed in claim 14, wherein thecoined part of the wire portion has a flat surface, and step (e) bondsthe flat surface of the coined part to the bonding surface.
 17. Themethod as claimed in claim 14, wherein the coined part of the wireportion has a patterned face of raised and recessed features, and step(e) bonds the patterned face of the coined part to the bonding surface.18. The method as claimed in claim 3, wherein the capillary face has agroove and the coining coins the part of the wire portion with thegroove and the capillary face.
 19. The method as claimed in claim 18,wherein the coining surface includes a groove having a depth less than adiameter of the wire portion and the coining of the wire portion isperformed to coin the part of the wire portion with the groove of thecoining surface.
 20. The method as claimed in claim 1, wherein the firstforming surface comprises a groove and step (b) includes moving thebonding tool face in the first direction along a length of the groovesuch that at least a part of the wire portion moves within the groove.21. The method as claimed in claim 1, further comprising after step (f),then forming an encapsulation layer overlying the one or more bondingsurface, wherein the encapsulation layer is formed so as to at leastpartially cover the bonding surface and the wire bonds, such that anunencapsulated portion of each wire bond is defined by a portion of atleast one of an end surface of such wire bond or of an edge surface ofsuch wire bond that is uncovered by the encapsulation layer.
 22. Themethod as claimed in claim 1, wherein the first forming surface is asurface of a forming element having an opening therein, wherein step (a)includes positioning the bonding tool such that the wire portion extendsat least partially into the opening.
 23. The method as claimed in claim22, wherein the opening includes a tapered portion adjacent to the firstforming surface, the tapered portion being configured to guide the wireportion towards a predetermined location of the first forming surface.24. The method as claimed in claim 22, wherein the first forming surfaceis a surface of a forming element having an opening therein, whereinstep (a) includes positioning the bonding tool such that the wireportion extends at least partially into the opening, and the openingincludes a tapered portion adjacent to the first forming surface, thetapered portion being configured to guide the wire portion into thegroove.
 25. The method as claimed in claim 1, wherein the wherein thefirst forming surface is a surface of a forming element having anopening therein, wherein step (c) includes moving the bonding tool intothe opening such that the wire portion extends at least partially intothe opening.
 26. The method as claimed in claim 25, wherein the coiningsurface is disposed within the opening.
 27. The method as claimed inclaim 22, wherein the opening is a first opening, and the formingelement includes a second opening, wherein step (c) includes moving thebonding tool into the second opening such that the wire portion extendsat least partially into the second opening.
 28. The method as claimed inclaim 27, wherein the coining surface is disposed within the secondopening.
 29. The method as claimed in claim 1, wherein a first wire bondof the wire bonds is adapted for carrying a first signal electricpotential and a second wire bond of the wire bonds is adapted forsimultaneously carrying a second signal electric potential differentfrom the first signal electric potential.
 30. The method as claimed inclaim 1, wherein the bonding surface is exposed at a surface of asubstrate when step (e) is performed to bond the coined surface to thebonding surface.
 31. The method as claimed in claim 25, furthercomprising mounting and electrically interconnecting a microelectronicelement with the substrate such that the microelectronic element iselectrically interconnected with at least some of the wire bonds. 32.The method as claimed in claim 1, wherein at least two of the wire bondsare bonded to a single bonding surface of the plurality of bondingsurfaces.